JP6468688B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

The present invention relates to a semiconductor device using a transistor. Or it relates to the driving method.

A semiconductor device such as a shift register is configured using a unipolar transistor, for example, using only an n-channel transistor rather than using both a p-channel transistor and an n-channel transistor. Thus, the manufacturing process can be simplified. Comprised of unipolar transistors, CMOS (Complement
A circuit having a function similar to that of (ary MOS) is also referred to as unipolar CMOS. A shift register configured using a unipolar transistor is disclosed in Patent Document 1, for example.

FIG. 7 is a circuit diagram illustrating a partial configuration of the shift register disclosed in Patent Document 1. In FIG. The shift register may have a configuration in which a plurality of stages 80 illustrated in FIG. 7 are provided and connected in cascade (cascade connection). Stage 80 includes transistor 81, transistor 82, transistor 8
3, a transistor 84, and a capacitor 85. The transistors (transistors 81 to 84) included in the stage 80 can all be n-channel transistors. Thus, all the transistors included in the shift register can be n-channel transistors.

In stage 80, the drain of transistor 81 is connected to terminal C1 and clock signal CL
K is entered. The source of the transistor 81 is connected to the output terminal OUT and the drain of the transistor 82. The signal output from the output terminal OUT becomes the output signal of the stage 80.
The gate of transistor 81 is connected to the source of transistor 83. Transistor 82
Are connected to the terminal VSS and supplied with a low power supply potential (eg, ground potential). The gate of the transistor 82 is connected to the terminal C2, and the clock inversion signal CLKB is input. Note that the clock inversion signal CLKB is an inversion signal (a signal whose logic value is inverted) of the clock signal CLK described above. The gate and drain of the transistor 83 are connected to the input terminal IN. The output signal of the previous stage 80 is input to the input terminal IN. The source of the transistor 83 is connected to the drain of the transistor 84. The source of the transistor 84 is connected to the terminal VSS and is supplied with a low power supply potential (for example, a ground potential). The gate of the transistor 84 is connected to the output terminal OUT of the subsequent stage (one stage later) stage 80. The capacitor element 85 is provided between the gate and the source of the transistor 81.

In the stage 80, the high level potential of the output signal becomes the high level potential of the clock signal CLK, and the low level potential of the output signal becomes the low power supply potential. A shift register having a plurality of stages 80 drives a plurality of loads using output signals sequentially output from the plurality of stages 80. For example,
In the case where a shift register is used for a scan line driver circuit of a display device, the load corresponds to a scan line, an element connected to the scan line, or the like.

JP 2006-24350 A

In the shift register disclosed in Patent Document 1, the high level potential of the output signal is the high level potential of the clock signal CLK. That is, the load (corresponding to an element driven by the shift register, a wiring to which a signal is input from the shift register, or the like) is driven by the high level potential of the clock signal CLK. Therefore, a circuit that generates the clock signal CLK (
Hereinafter, it is also referred to as a clock signal generation circuit. ) Requires a large current drive capability. In order to increase the current drive capability of a circuit, it is necessary to increase the size of the elements constituting the circuit (for example, the channel width and channel length of the transistor), and to provide a buffer composed of large-sized elements. The circuit area increases. Accordingly, an object of the present invention is to provide a shift register to which a clock signal generation circuit having a smaller current driving capability can be applied.

Note that the description of this problem does not disturb the existence of other problems. Other problems will be apparent from the description of the specification, drawings, claims, and the like.
Issues other than this can be extracted from the description of the drawings, the claims, and the like.

One embodiment of a semiconductor device of the present invention includes a switch and a logic circuit in which an input signal is input to an input terminal through the switch that is turned on. Note that a logic circuit is an input terminal (
In the case where there are a plurality of input terminals, a circuit (for example, an inverter circuit) that inverts the logical value of a signal input to the input terminal and outputs the inverted signal from the output terminal is shown. The switch is selected to be conductive or non-conductive by a clock signal (or its inverted signal). On the other hand, the logic circuit is supplied with a high power supply potential from a wiring (hereinafter also referred to as a high power supply line).
Further, a low power supply potential is supplied from another wiring (hereinafter also referred to as a low power supply line), and an electrical connection between the high power supply line and the output terminal and / or an electrical connection between the low power supply line and the output terminal is performed. By selecting an input terminal (if there are multiple input terminals, it corresponds to one of the multiple input terminals)
The logic value of the signal input to is inverted and output from the output terminal. The output of the logic circuit is used as the output of the semiconductor device. Thus, a load (for example, a bus line or an element connected to the bus line) driven by the semiconductor device is driven by being electrically connected to the high power line or the low power line. Note that the clock signal generation circuit may be included in the semiconductor device or an external circuit of the semiconductor device. Moreover, it is good also as a semiconductor device including load.

Here, all the transistors included in the semiconductor device can have the same conductivity type.
That is, all the transistors included in the switch and the logic circuit can have the same conductivity type. In this case, the logic circuit includes a bootstrap circuit, and the output signal is corrected using the bootstrap circuit. That is, all of the transistors included in the semiconductor device are n-channel transistors, and the logic circuit outputs a low power supply potential from the output terminal when the input signal is at a high level potential and the input signal is at a low level potential. In this case, a high power supply potential can be output from the output terminal by raising the potential of the output terminal using a bootstrap circuit. Alternatively, all the transistors included in the semiconductor device are p-channel transistors, and the logic circuit outputs a high power supply potential from the output terminal when the input signal is at a low level potential and the input signal is at a high level potential. In this case, a low power supply potential can be output from the output terminal by lowering the potential of the output terminal using a bootstrap circuit.

Further, the logic circuit can have a plurality of input terminals (an input terminal to which an input signal is input and an inverting input terminal to which a signal obtained by inverting the logic value of the input signal is input). The electrical connection between one of the high power line and the low power line and the output terminal is controlled by a signal input to the inverting input terminal, and the electrical connection between the other of the high power line and the low power line and the output terminal is controlled. By controlling with a signal input to the input terminal, the logic value of the input signal input to the input terminal can be inverted and output from the output terminal. For example, when a transistor included in the logic circuit is an n-channel transistor, the gate of the transistor provided between the high power supply line and the output terminal is electrically connected to the inverting input terminal, and the inverting input terminal is connected to the inverting input terminal. The on or off state of the transistor is controlled by the input signal, and the gate of another transistor provided between the low power supply line and the output terminal is electrically connected to the input terminal, and input to the input terminal By controlling the on state or off state of the transistor in accordance with the generated signal, the logic value of the input signal input to the input terminal can be inverted and output from the output terminal. Alternatively, for example, in the case where the transistor forming the logic circuit is a p-channel transistor, the gate of the transistor provided between the low power supply line and the output terminal is electrically connected to the inverting input terminal, and the inverting input terminal The on state or off state of the transistor is controlled by a signal input to the input terminal, and the gate of another transistor provided between the high power supply line and the output terminal is electrically connected to the input terminal. By controlling the on state or off state of the transistor in accordance with the input signal, the logic value of the input signal input to the input terminal can be inverted and output from the output terminal.

In addition, a transistor included in the semiconductor device includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes includes the semiconductor layer and the first gate. The insulating layer can overlap with each other, and the other of the pair of gate electrodes can overlap with the semiconductor layer and the second gate insulating layer. Here, one of the pair of gate electrodes is a gate of the transistor. The other of the pair of gate electrodes is also referred to as a back gate. The other of the pair of gate electrodes (back gate) can be electrically connected to the source of the transistor. Alternatively, in the case where the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) can be electrically connected to the low power supply line. In the case where the transistor is a p-channel transistor, the other of the pair of gate electrodes (back gate) can be electrically connected to the high power supply line. Note that one (gate) and the other (back gate) of the pair of gate electrodes may be electrically connected to serve as the gate of the transistor.

Note that each of the plurality of transistors included in the semiconductor device includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween. The first gate insulating layer overlaps with the other, and the other of the pair of gate electrodes overlaps with the semiconductor layer through the second gate insulating layer. In some of the plurality of transistors included in the semiconductor device, one of the pair of gate electrodes serves as a gate and the other of the pair of gate electrodes serves as a back gate. The one of the pair of gate electrodes may be a back gate and the other of the pair of gate electrodes may be a gate. That is, the positional relationship between the “gate” and the “back gate” can be reversed in some of the plurality of transistors included in the semiconductor device and the other transistors. For example, some of the plurality of transistors included in the semiconductor device are bottom-gate transistors with a gate provided below the semiconductor layer, and the other transistors among the plurality of transistors included in the semiconductor device are connected to the semiconductor layer. It is also possible to use a top gate transistor with a gate provided above. The back gate can be electrically connected to the source of the transistor. Alternatively, when the transistor is an n-channel transistor, the back gate can be electrically connected to the low power supply line. In the case where the transistor is a p-channel transistor, the back gate can be electrically connected to the high power supply line. Note that the gate and the back gate may be electrically connected to serve as the gate of the transistor.

For example, one embodiment of a semiconductor device of the present invention includes a switch and a logic circuit to which an input signal is input through the switch that is in a conductive state. The switch and all of the transistors included in the logic circuit Is an n-channel transistor, and the switch is selected to be conductive or non-conductive by a clock signal. The logic circuit has a bootstrap circuit, an input terminal to which an input signal is input, and a logical value of the input signal. An inverted input terminal to which an inverted signal is input, and an output terminal; a high power supply potential is supplied from a high power supply line; a low power supply potential is supplied from a low power supply line; By controlling the electrical connection with the signal input to the inverting input terminal and controlling the electrical connection between the low power line and the output terminal with the signal input to the input terminal, the input signal is In the case of a low-level potential, a low power supply potential is output from the output terminal, and when the input signal is a low-level potential, a high power supply potential is generated from the output terminal by raising the potential of the output terminal using a bootstrap circuit. The output n-channel transistor includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes is insulated from the semiconductor layer and the first gate insulation. The other of the pair of gate electrodes overlaps with the semiconductor layer and the second gate insulating layer, and the other of the pair of gate electrodes is electrically connected to the source.

Alternatively, for example, one embodiment of a semiconductor device of the present invention includes a switch and a logic circuit to which an input signal is input through the switch that is in a conductive state. All are p-channel transistors, and the switch is selected to be conductive or non-conductive according to the clock signal. An inverting input terminal to which an inverted signal is input, and an output terminal, a high power supply potential is supplied from a high power supply line, a low power supply potential is supplied from a low power supply line, The electrical connection is controlled by the signal input to the inverting input terminal, and the electrical connection between the high power supply line and the output terminal is controlled by the signal input to the input terminal. When the signal is at a low level potential, a high power supply potential is output from the output terminal. The power supply potential is output, and the p-channel transistor includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween. The other of the pair of gate electrodes overlaps with the semiconductor layer and the second gate insulating layer, and the other of the pair of gate electrodes is electrically connected to the source.

The semiconductor layer in which the channel of the transistor is formed can be formed using an oxide semiconductor. Note that silicon may be used. For example, it may be formed using amorphous silicon, may be formed using polycrystalline silicon, or may be formed using single crystal silicon.

One embodiment of the semiconductor device of the present invention may be a display device. For example, a display device using a liquid crystal element or a display device using a light emitting element such as an EL (electroluminescence) element may be used.

One embodiment of the semiconductor device of the present invention may be an image sensor.

One embodiment of the semiconductor device of the present invention may be an arithmetic circuit or a memory device. Note that the CPU and the programmable LSI are also included in the category of the arithmetic circuit.

One embodiment of the present invention can be an electronic device including the semiconductor device.

One embodiment of a semiconductor device of the present invention includes a switch and a logic circuit to which an input signal is input to an input terminal through the switch that is in a conductive state, and the switch is in a conductive state or a non-conductive state. Is selected by the clock signal (or its inverted signal). On the other hand, the logic circuit inverts the logical value of the input signal by selecting the electrical connection between the high power supply line and the output terminal and / or the electrical connection between the low power supply line and the output terminal. Output from. The output of the logic circuit is used as the output of the semiconductor device. Thus, the load driven by the semiconductor device is driven by being electrically connected to the high power line or the low power line. With such a structure, the semiconductor device has a high-level potential (or low-level potential) of the clock signal.
The clock signal generation circuit does not need a large current driving capability because the load is not driven using the. Therefore, the circuit area of the clock signal generation circuit can be reduced.

In addition, when all the transistors included in the semiconductor device have the same conductivity type, the manufacturing process of the semiconductor device can be simplified. Thus, the yield can be improved and the cost can be reduced. In this case, the logic circuit is configured to correct the output signal using a bootstrap circuit. In this way, even in a logic circuit configured using unipolar transistors, an output signal having an amplitude voltage (roughly) equal to the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential) can be obtained.

Furthermore, the logic circuit has a plurality of input terminals (an input terminal to which an input signal is input and an inverting input terminal to which a signal obtained by inverting the logic value of the input signal is input), and a high power line and a low power line The electrical connection between one of the output terminals and the output terminal is controlled by a signal input to the inverting input terminal, and the electrical connection between the other of the high power line and the low power line and the output terminal is controlled by a signal input to the input terminal. By doing so, the logic value of the input signal input to the input terminal can be inverted and output from the output terminal. Thus, even in a logic circuit configured using unipolar transistors, a transistor provided between the high power supply line and the output terminal, and a transistor provided between the low power supply line and the output terminal. When one of the two is on, the other can be off. Therefore, a through current in a circuit provided between the high power line and the low power line can be suppressed.

In addition, a transistor included in the semiconductor device includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes includes the semiconductor layer and the first gate. The insulating layer can overlap with each other, and the other of the pair of gate electrodes can overlap with the semiconductor layer and the second gate insulating layer. The other of the pair of gate electrodes (back gate) can be electrically connected to the source of the transistor. Alternatively, in the case where the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) can be electrically connected to the low power supply line. In the case where the transistor is a p-channel transistor, the other of the pair of gate electrodes (back gate) can be electrically connected to the high power supply line. Thus, the transistor can be prevented from being normally on. Therefore, malfunction of the semiconductor device can be suppressed and a through current can also be suppressed.

In this manner, a unipolar CMOS having a function similar to that of a CMOS can be realized using a unipolar transistor. The semiconductor device of the present invention can drive a load (such as a bus line) without requiring a large current driving capability for the clock signal generation circuit.

FIG. 3 illustrates a structure of a semiconductor device described in Embodiment 1; The figure which shows the structure of a logic circuit and a switch. FIG. 6 illustrates a semiconductor device including a plurality of stages. FIG. 6 illustrates a structure of a semiconductor device described in Embodiment 2; The figure which shows the structure of an amplifier circuit. FIG. 10 illustrates a structure of a semiconductor device described in Embodiment 3; FIG. 10 shows a structure of a conventional semiconductor device. FIG. 9 illustrates a structure example of a transistor. 10A and 10B illustrate an example of a method for manufacturing a transistor. FIG. 9 illustrates an electronic device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in the structures described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description thereof is not repeated.

Note that in the drawings, the size, the thickness, or the region is exaggerated for simplicity in some cases. Thus, one aspect of the embodiment of the present invention is not necessarily limited to the scale. Or, the figure schematically shows an ideal example. Thus, one aspect of the embodiment of the present invention is not limited to the shape shown in the drawings. For example, it is possible to include variation in shape due to manufacturing technology, variation in shape due to error, and the like.

Note that when X and Y are explicitly described as being connected, X and Y are electrically connected, and X and Y are functionally connected. , X and Y are directly connected. Here, X and Y are assumed to be objects (for example, devices, elements, circuits, wirings, electrodes, terminals, conductive films, layers, etc.). Therefore, it is not limited to a predetermined connection relationship, for example, the connection relationship shown in the figure or text, and includes things other than the connection relation shown in the figure or text.

As an example of the case where X and Y are electrically connected, an element (for example, a switch, a transistor, a capacitive element, an inductor, a resistance element, a diode, a display, etc.) that enables electrical connection between X and Y is shown. More than one element, light emitting element, load, etc.) can be connected between X and Y. Note that the switch has a function of controlling on / off. That is, the switch is in a conductive state (on state) or a non-conductive state (off state), and has a function of controlling whether or not to pass a current.

As an example of the case where X and Y are functionally connected, a circuit (for example, a logic circuit (an inverter, a NAND circuit, a NOR circuit, etc.) that enables a functional connection between X and Y, signal conversion, etc. Circuit (DA conversion circuit, AD conversion circuit, gamma correction circuit, etc.), potential level conversion circuit (power supply circuit (boost circuit, step-down circuit, etc.), level shifter circuit that changes signal potential level, etc.)
, Voltage source, current source, switching circuit, amplifier circuit (circuit that can increase signal amplitude or current amount, operational amplifier, differential amplifier circuit, source follower circuit, buffer circuit, etc.), signal generation circuit, memory circuit, control circuit, etc. ) Can be connected between X and Y. As an example, even if another circuit is interposed between X and Y, if the signal output from X is transmitted to Y, X and Y are functionally connected. To do.

Note that when X and Y are explicitly described as being connected, X and Y are electrically connected, and X and Y are functionally connected. , X and Y are directly connected. That is, when it is explicitly described that it is electrically connected, it is the same as when it is explicitly only described that it is connected.

In addition, even if it is a case where it is illustrated in the circuit diagram so that independent components are electrically connected to each other, actually, for example, when a part of the wiring also functions as an electrode, etc. In some cases, one conductive layer has the functions of a plurality of components such as wirings and electrodes. In this specification, the term “electrically connected” includes such a case where one conductive layer has functions of a plurality of components.

(Embodiment 1)
In this embodiment, a specific embodiment of a semiconductor device of the present invention will be described with reference to FIGS.

The semiconductor device can be configured to include the stage 10 shown in FIG. The stage 10 includes an input terminal IN, an inverting input terminal INB, a switch SW1, a switch SW2, and a switch SW3.
A switch SW4, a logic circuit INV1, a logic circuit INV2, a logic circuit INV3, a logic circuit INV4, an output terminal OUT, and an inverting output terminal OUTB.

The logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 each have an input terminal IN, an inverting input terminal INB, and an output terminal OUT, and invert the signal input to the input terminal IN. Output from the output terminal OUT. The logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 can also be referred to as inverter circuits. The output terminal OUT of the logic circuit INV1 is connected to the input terminal IN and the logic circuit I of the logic circuit INV3.
It is connected to the inverting input terminal INB and output terminal OUT of NV4. The output terminal OUT of the logic circuit INV2 is connected to the inverting input terminal INB of the logic circuit INV3, the input terminal IN of the logic circuit INV4, and the inverting output terminal OUTB. Each of the switch SW1, the switch SW2, the switch SW3, and the switch SW4 has a function of selecting a conduction state or a non-conduction state between the terminal A and the terminal B by a signal input to the terminal X. Thus, switch S
W1 has a function of selecting a conduction state or a non-conduction state between the input terminal IN and the input terminal IN of the logic circuit INV1 and the inverting input terminal INB of the logic circuit INV2 by a signal input to the terminal X. The switch SW2 has a function of selecting a conduction state or non-conduction state between the inverting input terminal INB and the inverting input terminal INB of the logic circuit INV1 and the input terminal IN of the logic circuit INV2 according to a signal input to the terminal X. Have. The terminals X of the switches SW1 and SW2 are connected to the terminal C1, and one of the clock signal and its inverted signal is input to the terminal C1. The switch SW3 selects a conduction state or a non-conduction state between the output terminal OUT of the logic circuit INV3 and the input terminal IN of the logic circuit INV1 and the inverting input terminal INB of the logic circuit INV2 according to a signal input to the terminal X It has the function to do. Switch SW
4 selects a conduction state or non-conduction state between the output terminal OUT of the logic circuit INV4 and the inverting input terminal INB of the logic circuit INV1 and the input terminal IN of the logic circuit INV2 according to a signal input to the terminal X. It has a function. The terminals X of the switches SW3 and SW4 are connected to the terminal C2, and the other of the clock signal and its inverted signal is input to the terminal C2.

In the stage 10 shown in FIG. 1, the switch SW1 is generated by a clock signal (or its inverted signal).
When the switch SW2 is conductive, the inverted signal of the clock signal (or the clock signal)
Thus, the switch SW3 and the switch SW4 are turned off, and when the switch SW1 and the switch SW2 are turned off by the clock signal (or its inverted signal), the switch SW3 and the switch SW4 are turned on by the inverted signal (or clock signal) of the clock signal. It becomes a conductive state. Therefore, it has a function of holding a signal input to the input terminal IN in synchronization with the clock signal. Therefore, the stage 10 illustrated in FIG. 1 can also be called a flip-flop circuit or a latch circuit.

One mode of more specific structures of the logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 will be described with reference to FIGS.

The logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 can each be the logic circuit INV illustrated in FIG. The logic circuit INV illustrated in FIG. 2A includes a transistor 101, a transistor 102, a transistor 103, and a capacitor 211. The gate of the transistor 101 is connected to the power supply line V1 to which the power supply potential V1 is applied, the drain of the transistor 101 is connected to the inverting input terminal INB,
The source of the transistor 101 is connected to the gate of the transistor 102 and the transistor 1
The drain of 02 is connected to the power supply line V1 to which the power supply potential V1 is applied, and the transistor 102
Is connected to the output terminal OUT, the gate of the transistor 103 is connected to the input terminal IN, the source of the transistor 103 is connected to the power supply line V2 to which the power supply potential V2 different from the power supply potential V1 is applied, and the drain of the transistor 103 is connected. Is connected to the output terminal OUT. One of the pair of electrodes of the capacitor 211 is connected to the gate of the transistor 102;
The other of the pair of electrodes of the capacitor 211 is connected to the source of the transistor 102.
Note that the parasitic capacitance of the transistor 102 can be positively used instead of providing the capacitor 211.

The transistor 101, the transistor 102, and the transistor 103 can be transistors having the same conductivity type. In the case where the transistors 101, 102, and 103 are n-channel transistors, the power supply potential V1 is higher than the power supply potential V2. Further, the power supply potential V2 is, for example, a ground potential. That is, the power supply potential V1 is a high power supply potential and the power supply potential V2 is a low power supply potential. Transistor 101, transistor 102
When the transistor 103 is a p-channel transistor, the power supply potential V1 is set lower than the power supply potential V2. Further, the power supply potential V1 is, for example, a ground potential. That is, the power supply potential V1 is a low power supply potential and the power supply potential V2 is a high power supply potential.

Each of the transistor 101, the transistor 102, and the transistor 103 includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes includes the semiconductor layer and the first layer. The gate insulating layer overlaps with the other, and the other of the pair of gate electrodes can overlap with the semiconductor layer with the second gate insulating layer interposed therebetween. Here, one of the pair of gate electrodes is a gate of the transistor. The other of the pair of gate electrodes is also referred to as a back gate. The other of the pair of gate electrodes (back gate) can be connected to the source of the transistor. FIG. 2A schematically illustrates a structure in which each of the transistor 101, the transistor 102, and the transistor 103 includes a gate and a back gate, and the back gate is connected to a source. Note that the other (back gate) of the pair of gate electrodes can be connected to the power supply line V2. That is, when the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) is connected to the low power supply line, and when the transistor is a p-channel transistor, the other of the pair of gate electrodes (back Gate) can be connected to the high power supply line. In this manner, each transistor (the transistor 101, the transistor 102, and the transistor 103) can be prevented from being normally on.

Note that in some of the transistors 101, 102, and 103, one of the pair of gate electrodes serves as a gate and the other of the pair of gate electrodes serves as a back gate. The one of the pair of gate electrodes may be a back gate and the other of the pair of gate electrodes may be a gate. For example, the transistor 102 may include one of a pair of gate electrodes as a gate, the other of a pair of gate electrodes as a back gate, and the transistor 103 may have one of a pair of gate electrodes as a back gate and the other of a pair of gate electrodes as a gate. Good. That is, the positional relationship between the “gate” and the “back gate” can be reversed between the transistor 102 and the transistor 103. For example, one of the transistor 102 and the transistor 103 is a bottom-gate transistor in which a gate is provided below a semiconductor layer, and the transistor 1
The other of 02 and the transistor 103 can be a top-gate transistor in which a gate is provided above a semiconductor layer. The back gate can be electrically connected to the source of the transistor. Alternatively, when the transistor is an n-channel transistor, the back gate can be electrically connected to the low power supply line. In the case where the transistor is a p-channel transistor, the back gate can be electrically connected to the high power supply line.

An operation of the logic circuit INV illustrated in FIG.

First, operation in the case where the transistors 101, 102, and 103 are n-channel transistors is described. When a high-level potential is input to the input terminal IN and a low-level potential is input to the inverting input terminal INB, the transistor 103 is turned on and the transistor 102 is turned off. Thus, the output terminal OUT is connected to the power supply line V2, and the power supply potential V2 (low power supply potential) is output from the output terminal OUT.
When a low level potential is input to the input terminal IN and a high level potential is input to the inverting input terminal INB, the transistor 103 is turned off and the transistor 102 is turned on. Thus, the output terminal OUT is connected to the power supply line V1. Here, the inverting input terminal IN
When a high level potential is input to B, the source potential of the transistor 101 becomes a predetermined potential (the transistor 1 with respect to the power source potential V1 which is the gate potential of the transistor 101).
The transistor 101 is turned off and its source is in a floating state. After that, the potential of the source of the transistor 102 continues to rise, so that the potential of the gate of the transistor 102 rises due to capacitive coupling by the capacitor 211. Thus, the potential of the output terminal OUT is raised to the power supply potential V1 (or a potential close thereto), and the power supply potential V1 (high power supply potential) is output from the output terminal OUT. That is, it can be said that the logic circuit INV illustrated in FIG. 2A includes a bootstrap circuit.

Next, operation in the case where the transistors 101, 102, and 103 are p-channel transistors is described. When a low level potential is input to the input terminal IN and a high level potential is input to the inverting input terminal INB, the transistor 103 is turned on and the transistor 102 is turned off. Thus, the output terminal OUT is connected to the power supply line V2, and the power supply potential V2 (high power supply potential) is output from the output terminal OUT. When a high level potential is input to the input terminal IN and a low level potential is input to the inverting input terminal INB, the transistor 103 is turned off and the transistor 102 is turned on. Thus, the output terminal OUT is connected to the power supply line V1. Here, the inverting input terminal I
When a low-level potential is input to NB, the source potential of the transistor 101 becomes a predetermined potential (a potential higher than the power supply potential V1 that is the gate potential of the transistor 101 by the threshold voltage of the transistor 101). Is turned off and its source is in a floating state. After that, the potential of the source of the transistor 102 continues to decrease, so that the transistor 102 is capacitively coupled by the capacitor 211.
The potential of the gate decreases. Thus, the potential of the output terminal OUT is lowered to the power supply potential V1 (or a potential close thereto), and the power supply potential V1 (low power supply potential) is output from the output terminal OUT. That is, it can be said that the logic circuit INV illustrated in FIG. 2A includes a bootstrap circuit.

Each of the logic circuit INV1 and the logic circuit INV2 is the logic circuit INV illustrated in FIG.
The logic circuit INV3 and the logic circuit INV4 can be the logic circuit INV illustrated in FIG. The logic circuit INV illustrated in FIG. 2B includes the transistor 104 and the transistor 105. The gate of the transistor 104 is connected to the inverting input terminal INB, the drain of the transistor 104 is connected to the power supply line V1 to which the power supply potential V1 is applied, the source of the transistor 104 is connected to the output terminal OUT, and the gate of the transistor 105 is input terminal Connected to IN, the source of the transistor 105 is connected to a power supply line V2 to which a power supply potential V2 different from the power supply potential V1 is applied, and the drain of the transistor 105 is connected to the output terminal OUT.

The transistor 104 and the transistor 105 can be transistors of the same conductivity type. In the case where the transistors 104 and 105 are n-channel transistors, the power supply potential V1 is higher than the power supply potential V2. Further, the power supply potential V2 is, for example, a ground potential. That is, the power supply potential V1 is a high power supply potential and the power supply potential V2 is a low power supply potential. In the case where the transistors 104 and 105 are p-channel transistors,
The power supply potential V1 is set lower than the power supply potential V2. Further, the power supply potential V1 is, for example, a ground potential. That is, the power supply potential V1 is a low power supply potential and the power supply potential V2 is a high power supply potential.

Each of the transistor 104 and the transistor 105 includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween. One of the pair of gate electrodes is the semiconductor layer and the first gate insulating layer. The other of the pair of gate electrodes can overlap with the semiconductor layer and the second gate insulating layer. Here, one of the pair of gate electrodes is a gate of the transistor. The other of the pair of gate electrodes is also referred to as a back gate. The other of the pair of gate electrodes (back gate) can be connected to the source of the transistor. FIG. 2B schematically illustrates a structure in which each of the transistor 104 and the transistor 105 includes a gate and a back gate, and the back gate is connected to a source. Note that the other (back gate) of the pair of gate electrodes can be connected to the power supply line V2. That is, when the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) is connected to the low power supply line, and when the transistor is a p-channel transistor, the other of the pair of gate electrodes (back Gate) can be connected to the high power supply line. Thus, each transistor (transistor 104 and transistor 1
05) can be prevented from becoming normally-on.

Note that one of the transistor 104 and the transistor 105 has one of a pair of gate electrodes as a gate, the other of the pair of gate electrodes has a back gate, and the other of the transistor 104 and the transistor 105 has one of a pair of gate electrodes. A back gate may be used, and the other of the pair of gate electrodes may be a gate. For example, in the transistor 104, one of the pair of gate electrodes serves as a gate, the other of the pair of gate electrodes serves as a back gate, and the transistor 10
In 5, one of the pair of gate electrodes may be a back gate and the other of the pair of gate electrodes may be a gate. That is, the positional relationship between the “gate” and the “back gate” can be reversed between the transistor 104 and the transistor 105. For example, one of the transistor 104 and the transistor 105 is a bottom-gate transistor with a gate provided below the semiconductor layer, and the other of the transistor 104 and the transistor 105 is a top-gate transistor with a gate provided above the semiconductor layer. It is also possible. The back gate can be electrically connected to the source of the transistor. Alternatively, when the transistor is an n-channel transistor, the back gate can be electrically connected to the low power supply line. In the case where the transistor is a p-channel transistor, the back gate can be electrically connected to the high power supply line.

An operation of the logic circuit INV illustrated in FIG. 2B is described.

First, operation in the case where the transistors 104 and 105 are n-channel transistors is described. A high level potential is input to the input terminal IN, and the inverting input terminal I
When a low-level potential is input to NB, the transistor 104 is turned off and the transistor 105 is turned on. Thus, the output terminal OUT is connected to the power supply line V2, and the power supply potential V2 (low power supply potential) is output from the output terminal OUT. When a low level potential is input to the input terminal IN and a high level potential is input to the inverting input terminal INB, the transistor 104 is turned on and the transistor 105 is turned off. Thus, the output terminal OUT is connected to the power supply line V1. However, the potential output from the output terminal OUT is
It cannot be made higher than a high potential (for example, power supply potential V1) input to the inverting input terminal INB by a threshold voltage lower than that of the transistor 104.

Next, operation in the case where the transistors 104 and 105 are p-channel transistors is described. When a low level potential is input to the input terminal IN and a high level potential is input to the inverting input terminal INB, the transistor 104 is turned off and the transistor 105 is turned on. Thus, the output terminal OUT is connected to the power supply line V2, and the power supply potential V2 (high power supply potential) is output from the output terminal OUT. When a high level potential is input to the input terminal IN and a low level potential is input to the inverting input terminal INB, the transistor 104 is turned on and the transistor 105 is turned off. Thus, the output terminal OUT is connected to the power supply line V1. However, the potential output from the output terminal OUT cannot be lower than the potential that is higher by the threshold voltage of the transistor 104 than the low-level potential (for example, the power supply potential V1) input to the inverting input terminal INB.

As described above, the logic circuit INV illustrated in FIG. 2B is also a circuit that inverts the logic value of the signal input to the input terminal IN and outputs the inverted signal from the output terminal OUT, and can also be referred to as an inverter circuit. However, it does not have a bootstrap circuit. Therefore, the logic circuit INV illustrated in FIG. 2B outputs an output signal having a predetermined amplitude equal to the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, equivalent to | V1−V2 |). Can not do it. However, FIG.
The circuit configuration can be simplified compared to the logic circuit INV having the bootstrap circuit shown in FIG.

Here, in FIG. 1, the output of the logic circuit INV3 and the output of the logic circuit INV4 are input to the logic circuit INV1 and the logic circuit INV2 via the switch SW3 and the switch SW4, and the output signal of the logic circuit INV1 and the logic circuit INV2 Output signal is output terminal OU of each stage
It becomes an output signal from T and the inverted output terminal OUTB. For this reason, the logic circuit INV3 and the logic circuit INV4 correspond to the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, | V1−V
2), the output of the logic circuit INV3 and the output of the logic circuit INV4 are amplified by the logic circuit INV1 and the logic circuit INV2. From the output terminal OUT and the inverted output terminal OUTB, an output signal having an amplitude equal to (approximately) the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, corresponding to | V1−V2 |) is output. In this way, a semiconductor device capable of outputting a signal having a predetermined amplitude while further simplifying the circuit configuration of the semiconductor device is obtained.

In FIG. 1, each of the switch SW1 and the switch SW2 can be a switch SW including a transistor 106 as shown in FIG. Transistor 1
The gate of 06 can be connected to the terminal X, one of the source and the drain of the transistor 106 can be connected to the terminal A, and the other of the source and the drain can be connected to the terminal B. The transistor 106 includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes overlaps with the semiconductor layer and the first gate insulating layer. In addition, the other of the pair of gate electrodes can overlap with the semiconductor layer with the second gate insulating layer interposed therebetween. Here, one of the pair of gate electrodes is a gate of the transistor. The other of the pair of gate electrodes is also referred to as a back gate. The other of the pair of gate electrodes (back gate) can be connected to the power supply line V2. FIG. 2C schematically illustrates a structure in which the transistor 106 includes a gate and a back gate, and the back gate is connected to the power supply line V2. That is, when the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) is connected to the low power supply line, and when the transistor is a p-channel transistor, the other of the pair of gate electrodes (back Gate)
Can be connected to a high power line. Note that in the transistor 106, the other of the pair of gate electrodes (back gate) can be connected to the source of the transistor. Thus, the transistor 106 can be prevented from being normally on.

In FIG. 1, each of the switch SW3 and the switch SW4 can be a switch SW including a transistor 107 as shown in FIG. Transistor 1
The gate of 07 can be connected to the terminal X, one of the source and the drain of the transistor 107 can be connected to the terminal A, and the other of the source and the drain can be connected to the terminal B. The transistor 107 includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes overlaps with the semiconductor layer and the first gate insulating layer. In addition, the other of the pair of gate electrodes can overlap with the semiconductor layer with the second gate insulating layer interposed therebetween. Here, one of the pair of gate electrodes is a gate of the transistor. The other of the pair of gate electrodes is also referred to as a back gate. FIG. 2D schematically illustrates a structure in which the transistor 107 includes a gate and a back gate, and the back gate is connected to the power supply line V2. That is, when the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) is connected to the low power supply line, and when the transistor is a p-channel transistor, the other of the pair of gate electrodes (back Gate) can be connected to the high power supply line. Note that in the transistor 107, the other of the pair of gate electrodes (back gate) can be connected to the source of the transistor. Thus, the transistor 107 can be prevented from being normally on.

Here, since the switch may have a smaller current driving capability than the logic circuit, the size of the transistor constituting the switch can be made smaller than the size of the transistor constituting the logic circuit. In other words, the channel width (hereinafter also referred to as W or gate width) of the transistor 106 and the transistor 107 (or the ratio of channel width to the channel length (hereinafter also referred to as L or gate length) (W / L)) The channel width (W) (or the ratio of the channel width to the channel length (L) (W / L)) of any or all of the transistor 102, the transistor 103, the transistor 104, and the transistor 105 can be reduced. Thus, high definition and small size of the semiconductor device can be achieved.

Since the logic circuit INV3 and the logic circuit INV4 do not directly drive the load connected to the output terminal OUT, the current drive capability may be smaller than that of the logic circuit INV1 and the logic circuit INV2. Therefore, the channel width (W) (or the channel length (or the channel length) of the transistors included in the logic circuits INV3 and INV4 (the transistors 101, 102, and 103, particularly the transistors 102 and 103, or the transistors 104 and 105) L) is the ratio of the channel width (W / L)) to the transistors (transistor 101, transistor 102, and transistor 103, in particular, transistor 102 and transistor 103, which constitute the logic circuit INV1 and the logic circuit INV2.
) Channel width (W) (or ratio of channel width to channel length (L) (W / L))
Can be made smaller. Thus, high definition and small size of the semiconductor device can be achieved.

In the logic circuit INV illustrated in FIG. 2A, since the transistor 101 does not directly drive the load connected to the output terminal OUT, the current driving capability may be smaller than those of the transistor 102 and the transistor 103. Therefore, the channel width (W) of the transistor 101 (or the ratio of the channel width to the channel length (L) (W / L)) is equal to the channel width (W) of the transistor 102 and the transistor 103 (or channel length (L)). The channel width ratio to (W / L) can be made smaller.

One embodiment of the semiconductor device of the present invention can have a structure including a plurality of stages 10 illustrated in FIGS. For example, as illustrated in FIG. 3, the semiconductor device 100 includes a plurality of stages 10.
A configuration in which the input terminal IN is connected to the preceding output terminal OUT and the inverting input terminal INB is connected to the preceding inverting output terminal OUTB in a cascade connection (cascade connection) may be employed. Here, the logical value of the signal input to the terminal C1 can be made different in the adjacent stages of the plurality of stages 10 (that is, in the adjacent stage of the plurality of stages 10, the terminal C2
The logic value of the signal input to can be different). For example, in a certain stage 10,
A clock signal is input to the terminal C1, and a clock inversion signal is input to the terminal C2.
In the stage 10 adjacent to 0, a clock inversion signal can be input to the terminal C1 and a clock signal can be input to the terminal C2. In FIG. 3, the clock signal is indicated by CLK, and its inverted signal is indicated by CLKB. In addition, inverted signals can be input to the input terminal IN and the inverting input terminal INB of the first stage among the plurality of stages 10 connected in cascade. In FIG. 3, the signal SP is input to the input terminal IN of the first stage, and the inverted input terminal INB
Is inputted with an inverted signal SPB of the signal SP.

The semiconductor device 100 illustrated in FIG. 3 has a function of sequentially holding the signal input to the input terminal IN of the first stage in each stage 10 in synchronization with the clock signal. Therefore, the semiconductor device 100 can also be referred to as a shift register. The signal SP can also be called a start pulse. The semiconductor device 100 sequentially shifts the start pulse in synchronization with the clock signal CLK, and outputs the output SR1.
, SR2, SR3, and so on. The semiconductor device 100 has outputs SR1, S
The load can be driven by R2 and SR3. Outputs SR1, SR2, SR
3 is an output signal from the output terminal OUT of each stage 10, but is not limited thereto. For example, output signals from the inverting output terminal OUTB of each stage 10 may be used as the outputs SR1, SR2, SR3. Furthermore, only the outputs SR2, SR4, SR6 of the even-numbered stage 10 may be used as the output of the semiconductor device 100 to drive the load.

In the semiconductor device described in this embodiment, the switches (switch SW1, switch SW1
2, a switch SW3, a switch SW4), and a logic circuit (a logic circuit INV1, a logic circuit INV2, a logic circuit INV3, and a logic circuit INV4) in which an input signal is input to the input terminal through the switch that is in a conductive state. In the switch, the conductive state or the non-conductive state is selected by a clock signal (or its inverted signal). On the other hand, the logic circuit inverts the logical value of the input signal and outputs it from the output terminal by selecting the connection between the high power supply line and the output terminal and the connection between the low power supply line and the output terminal. The output of the logic circuit is used as the output of the semiconductor device. Thus, the load driven by the semiconductor device is driven by being connected to the high power line or the low power line. With such a configuration, the semiconductor device does not drive the load using the high-level potential (or low-level potential) of the clock signal, so that the clock signal generation circuit does not require a large current driving capability. Therefore, the circuit area of the clock signal generation circuit can be reduced.

In addition, when all the transistors included in the semiconductor device have the same conductivity type, the manufacturing process of the semiconductor device can be simplified. Thus, the yield can be improved and the cost can be reduced. In this case, logic circuits (logic circuit INV1, logic circuit INV2,
All of the logic circuit INV3 and the logic circuit INV4, or only the logic circuit INV3 and the logic circuit INV4) are configured to correct the output signal using a bootstrap circuit. In this way, even in a logic circuit configured using unipolar transistors, an output signal having an amplitude voltage (roughly) equal to the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential) can be obtained.

Furthermore, the logic circuit has a plurality of input terminals (an input terminal to which an input signal is input and an inverting input terminal to which a signal obtained by inverting the logic value of the input signal is input), and a high power line and a low power line By controlling the connection between one of the output terminal and the output terminal by a signal input to the inverting input terminal, and controlling the connection between the other of the high power line and the low power line and the output terminal by a signal input to the input terminal, The logic value of the input signal input to the input terminal can be inverted and output from the output terminal. Thus, even in a logic circuit configured using unipolar transistors, a transistor provided between the high power supply line and the output terminal, and a transistor provided between the low power supply line and the output terminal. When one of the two is on, the other can be off. Therefore, a through current in a circuit provided between the high power line and the low power line can be suppressed.

In addition, a transistor included in the semiconductor device includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes includes the semiconductor layer and the first gate. The insulating layer can overlap with each other, and the other of the pair of gate electrodes can overlap with the semiconductor layer and the second gate insulating layer. The other of the pair of gate electrodes (back gate) can be connected to the source of the transistor. Alternatively, in the case where the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) can be connected to the low power supply line. In the case where the transistor is a p-channel transistor, the other of the pair of gate electrodes (back gate) can be connected to a high power supply line. Thus, each transistor can be prevented from being normally on. Therefore, malfunction of the semiconductor device can be suppressed and a through current can also be suppressed.

This embodiment can be implemented freely combining with any of the other embodiments.

(Embodiment 2)
In this embodiment, a specific embodiment of a semiconductor device of the present invention will be described with reference to FIGS.

The semiconductor device can have a structure having a stage 10 shown in FIG. The stage 10 includes an input terminal IN, an inverting input terminal INB, a switch SW1, a switch SW2, and a switch SW3.
A switch SW4, a logic circuit INV1, a logic circuit INV2, a logic circuit INV3, a logic circuit INV4, an amplifier circuit BUF1, an amplifier circuit BUF2, an output terminal OUT,
And an inverting output terminal OUTB.

The logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 each have an input terminal IN, an inverting input terminal INB, and an output terminal OUT, and invert the signal input to the input terminal IN. Output from the output terminal OUT. The logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 can also be referred to as inverter circuits. Each of the amplifier circuit BUF1 and the amplifier circuit BUF2 includes an input terminal IN and an inverting input terminal I.
It has NB and an output terminal OUT, and impedance-converts the signal input to the input terminal IN (lowers the impedance) and outputs it from the output terminal OUT. The output terminal OUT of the logic circuit INV1 is connected to the input terminal IN of the amplifier circuit BUF1 and the inverting input terminal INB of the amplifier circuit BUF2. The output terminal OUT of the logic circuit INV2 is connected to the inverting input terminal INB of the amplifier circuit BUF1 and the input terminal IN of the amplifier circuit BUF2. The output terminal OUT of the amplifier circuit BUF1 is connected to the input terminal IN of the logic circuit INV3, the inverting input terminal INB of the logic circuit INV4, and the output terminal OUT. The output terminal OUT of the amplifier circuit BUF2 is connected to the inverting input terminal INB of the logic circuit INV3, the input terminal IN of the logic circuit INV4, and the inverting output terminal OUTB. Each of the switch SW1, the switch SW2, the switch SW3, and the switch SW4 has a function of selecting a conduction state or a non-conduction state between the terminal A and the terminal B by a signal input to the terminal X. Thus, the switch SW1 is connected to the input terminal IN.
And a function of selecting a conduction state or a non-conduction state between the input terminal IN of the logic circuit INV1 and the inverting input terminal INB of the logic circuit INV2 by a signal input to the terminal X.
The switch SW2 has a function of selecting a conduction state or non-conduction state between the inverting input terminal INB and the inverting input terminal INB of the logic circuit INV1 and the input terminal IN of the logic circuit INV2 according to a signal input to the terminal X. Have. The terminals X of the switches SW1 and SW2 are connected to the terminal C1, and one of the clock signal and its inverted signal is input to the terminal C1. The switch SW3 includes an output terminal OUT of the logic circuit INV3 and an input terminal I of the logic circuit INV1.
N and the inverting input terminal INB of the logic circuit INV2 have a function of selecting a conduction state or a non-conduction state between them by a signal inputted to the terminal X. The switch SW4 is connected to the logic circuit INV
4 has a function of selecting a conduction state or a non-conduction state between the output terminal OUT 4 and the inverting input terminal INB of the logic circuit INV1 and the input terminal IN of the logic circuit INV2 by a signal input to the terminal X. The terminals X of the switch SW3 and the switch SW4 are connected to the terminal C2,
The other of the clock signal and its inverted signal is input to the terminal C2.

In the stage 10 shown in FIG. 4, the switch SW1 is generated by a clock signal (or its inverted signal).
When the switch SW2 is conductive, the inverted signal of the clock signal (or the clock signal)
Thus, the switch SW3 and the switch SW4 are turned off, and when the switch SW1 and the switch SW2 are turned off by the clock signal (or its inverted signal), the switch SW3 and the switch SW4 are turned on by the inverted signal (or clock signal) of the clock signal. It becomes a conductive state. Therefore, it has a function of holding a signal input to the input terminal IN in synchronization with the clock signal. Therefore, the stage 10 illustrated in FIG. 4 can also be called a flip-flop circuit or a latch circuit.

One mode of more specific structures of the amplifier circuit BUF1 and the amplifier circuit BUF2 will be described with reference to FIG.

Each of the amplifier circuit BUF1 and the amplifier circuit BUF2 can be the amplifier circuit BUF shown in FIG. The amplifier circuit BUF shown in FIG. 5 includes a transistor 108 and a transistor 10.
9, a transistor 110, and a capacitor 212. The gate of the transistor 108 is connected to the power supply line V1 to which the power supply potential V1 is applied, the drain of the transistor 108 is connected to the input terminal IN, the source of the transistor 108 is connected to the gate of the transistor 109, and the drain of the transistor 109 is power supply potential Connected to the power supply line V1 to which V1 is applied, the source of the transistor 109 is connected to the output terminal OUT, the gate of the transistor 110 is connected to the inverting input terminal INB, and the source of the transistor 110 is a power supply potential V2 different from the power supply potential V1. Is connected to the power supply line V2, and the drain of the transistor 110 is connected to the output terminal OUT. One of the pair of electrodes of the capacitor 212 is connected to the gate of the transistor 109, and the other of the pair of electrodes of the capacitor 212 is connected to the source of the transistor 109. Note that parasitic capacitance or the like of the transistor 109 can be positively used instead of providing the capacitor 212.

The transistors 108, 109, and 110 can be transistors having the same conductivity type. In the case where the transistors 108, 109, and 110 are n-channel transistors, the power supply potential V1 is higher than the power supply potential V2. Further, the power supply potential V2 is, for example, a ground potential. That is, the power supply potential V1 is a high power supply potential and the power supply potential V2 is a low power supply potential. Transistor 108, transistor 109
When the transistor 110 is a p-channel transistor, the power supply potential V1 is lower than the power supply potential V2. Further, the power supply potential V1 is, for example, a ground potential. That is, the power supply potential V1 is a low power supply potential and the power supply potential V2 is a high power supply potential.

Each of the transistor 108, the transistor 109, and the transistor 110 includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes includes the semiconductor layer and the first layer. The gate insulating layer overlaps with the other, and the other of the pair of gate electrodes can overlap with the semiconductor layer with the second gate insulating layer interposed therebetween. Here, one of the pair of gate electrodes is a gate of the transistor. The other of the pair of gate electrodes is also referred to as a back gate. The other of the pair of gate electrodes (back gate) can be connected to the source of the transistor. FIG. 5 schematically illustrates a configuration in which each of the transistor 108, the transistor 109, and the transistor 110 includes a gate and a back gate, and the back gate is connected to a source. Note that the other (back gate) of the pair of gate electrodes can be connected to the power supply line V2. That is, the transistor is n
In the case of a channel-type transistor, the other of the pair of gate electrodes (back gate) is connected to a low power supply line. Can also be connected. In this manner, each transistor (the transistor 108, the transistor 109, and the transistor 110) can be prevented from being normally on.

Note that in some of the transistors 108, 109, and 110, one of the pair of gate electrodes serves as a gate and the other of the pair of gate electrodes serves as a back gate, and the other transistors of the transistor 108, the transistor 109, and the transistor 110 The one of the pair of gate electrodes may be a back gate and the other of the pair of gate electrodes may be a gate. For example, the transistor 109 may have one of a pair of gate electrodes as a gate, the other of a pair of gate electrodes as a back gate, and the transistor 110 may have one of a pair of gate electrodes as a back gate and the other of a pair of gate electrodes as a gate. Good. That is, the positional relationship between the “gate” and the “back gate” in the transistor 109 and the transistor 110 can be reversed. For example, one of the transistor 109 and the transistor 110 is a bottom-gate transistor in which a gate is provided below a semiconductor layer, and the transistor 1
The other of 09 and the transistor 110 can be a top gate transistor in which a gate is provided above a semiconductor layer. The back gate can be electrically connected to the source of the transistor. Alternatively, when the transistor is an n-channel transistor, the back gate can be electrically connected to the low power supply line. In the case where the transistor is a p-channel transistor, the back gate can be electrically connected to the high power supply line.

An operation of the amplifier circuit BUF shown in FIG. 5 will be described.

First, operation in the case where the transistors 108, 109, and 110 are n-channel transistors is described. When a low level potential is input to the input terminal IN and a high level potential is input to the inverting input terminal INB, the transistor 110 is turned on and the transistor 109 is turned off. Thus, the output terminal OUT is connected to the power supply line V2, and the power supply potential V2 (low power supply potential) is output from the output terminal OUT.
When a high level potential is input to the input terminal IN and a low level potential is input to the inverting input terminal INB, the transistor 110 is turned off and the transistor 109 is turned on. Thus, the output terminal OUT is connected to the power supply line V1. Here, when a high-level potential is input to the input terminal IN, the source potential of the transistor 108 is a predetermined potential (a potential lower than the power supply potential V1 that is the gate potential of the transistor 108 by the threshold voltage of the transistor 108). Then, the transistor 108 is turned off and its source is in a floating state. After that, the potential of the source of the transistor 109 continues to rise, so that the potential of the gate of the transistor 109 rises due to capacitive coupling by the capacitor 212. Thus, the potential of the output terminal OUT is raised to the power supply potential V1 (or a potential close thereto), and the power supply potential V1 (high power supply potential) is output from the output terminal OUT.
That is, it can be said that the amplifier circuit BUF shown in FIG. 5 includes a bootstrap circuit.

Next, operation in the case where the transistors 108, 109, and 110 are p-channel transistors is described. When a high level potential is input to the input terminal IN and a low level potential is input to the inverting input terminal INB, the transistor 110 is turned on and the transistor 109 is turned off. Thus, the output terminal OUT is connected to the power supply line V2, and the power supply potential V2 (high power supply potential) is output from the output terminal OUT. When a low level potential is input to the input terminal IN and a high level potential is input to the inverting input terminal INB, the transistor 110 is turned off and the transistor 109 is turned on. Thus, the output terminal OUT is connected to the power supply line V1. Here, when a low-level potential is input to the input terminal IN, the potential of the source of the transistor 108 is changed to a predetermined potential (the power supply potential V1 which is the gate potential of the transistor 108).
The transistor 108 is turned off and its source is in a floating state. After that, the potential of the source of the transistor 109 continues to decrease, so that the potential of the gate of the transistor 109 decreases due to capacitive coupling by the capacitor 212. Thus, the potential of the output terminal OUT is lowered to the power supply potential V1 (or a potential close thereto), and the power supply potential V1 (low power supply potential) is output from the output terminal OUT. That is, it can be said that the amplifier circuit BUF shown in FIG. 5 includes a bootstrap circuit.

Since the operation as described above is performed, the amplifier circuit BUF can also be referred to as a buffer circuit or a level shifter circuit.

Note that in FIG. 4, each of the logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 can have a structure similar to that of the logic circuit INV illustrated in FIG. As described in Embodiment 1, the circuit configuration of the logic circuit INV illustrated in FIG. 2B can be simplified as compared with the logic circuit INV illustrated in FIG. Voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, | V1-V2
It is impossible to output an output signal having a predetermined amplitude equal to |

However, in FIG. 4, the output of the logic circuit INV3 and the output of the logic circuit INV4 are input to the logic circuit INV1 and the logic circuit INV2 via the switch SW3 and the switch SW4. Further, the outputs of the logic circuit INV1 and the logic circuit INV2 are amplified by the amplifier circuit BUF1 and the amplifier circuit BUF2, and the output terminal OUT and the inverted output terminal OUTB of each stage 10 are amplified.
Output signal. Therefore, the logic circuit INV1, the logic circuit INV2, the logic circuit IN
Even if V3 and the logic circuit INV4 cannot output an output signal having an amplitude equal to (approximately) the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, equivalent to | V1−V2 |), From the output terminal OUT and the inverted output terminal OUTB of the stage 10, an output signal having an amplitude equal to (approximately) the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, corresponding to | V1−V2 |) is output. . Thus, a semiconductor device capable of outputting a signal having a predetermined amplitude is obtained.

Note that any or all of the logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 in FIG. 4 are the same as the logic circuit I illustrated in FIG.
A configuration similar to that of NV is also possible.

Further, each of the switch SW1 and the switch SW2 is shown in FIG.
Since it can be set as the structure similar to shown by, description is abbreviate | omitted. Each of the switch SW3 and the switch SW4 can have a structure similar to that illustrated in FIG. 2D in Embodiment 1, and thus description thereof is omitted.

Here, since the switch may have a smaller current driving capability than the logic circuit or the amplifier circuit, the size of the transistor constituting the switch can be made smaller than the size of the transistor constituting the logic circuit or the amplifier circuit. That is, the transistor 106 and the transistor 1
07 channel width (W) (or ratio of channel width to channel length (L) (W / L)
) Is the transistor 104, transistor 105, transistor 108, transistor 1
09 and the transistor 110 can be smaller than the channel width (W) (or the ratio of the channel width to the channel length (L) (W / L)). Thus, high definition and small size of the semiconductor device can be achieved.

Since the logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 do not directly drive the load connected to the output terminal OUT, the amplifier circuit BUF1 and the amplifier circuit B
The current driving capability may be smaller than that of UF2. Therefore, the logic circuit INV1, the logic circuit I
The channel width (W) (or the ratio of the channel width to the channel length (L) (W / L)) of the transistors (transistors 104 and 105) included in the NV2, the logic circuit INV3, and the logic circuit INV4 is an amplifier circuit. Channel width (W) (or ratio of channel width to channel length (L) (W / L) of transistors (transistor 108, transistor 109, and transistor 110, in particular transistor 109 and transistor 110) included in BUF1 and amplifier circuit BUF2 ). Thus,
High definition and miniaturization of a semiconductor device can be achieved.

The stage 10 having the configuration shown in FIG. 4 includes a logic circuit INV1, an amplifier circuit BUF1, and a logic circuit INV2 instead of the logic circuits INV1 and INV2 in the stage 10 having the configuration shown in FIG.
And an amplifier circuit BUF2. That is, the stage 10 of the configuration shown in FIG.
It can also be said that the logic circuit INV1 and the logic circuit INV2 in the stage 10 having the configuration shown in FIG. 1 correspond to a configuration separated into a circuit having a logic value inversion function and a circuit having an amplification function. Here, by separating the circuit having the logic value inversion function and the circuit having the amplification function, as described above, the circuit having the logic value inversion function (the logic circuit I in FIG. 4).
The size of the transistors constituting the NV1 and the logic circuit INV2) can be made smaller than the size of the transistors constituting the circuit having the amplification function (the amplification circuit BUF1 and the amplification circuit BUF2 in FIG. 4). Therefore, the current drive capability of a circuit (a switch SW1, a switch SW2, a switch SW3, a switch SW4, etc. in FIG. 4) that inputs a signal to a circuit having a logic value inversion function (a logic circuit INV1 and a logic circuit INV2 in FIG. 4) Can be small. Thus, high definition and small size of the semiconductor device can be achieved.

In the amplifier circuit BUF illustrated in FIG. 5, the transistor 108 does not directly drive a load connected to the output terminal OUT, and thus may have a smaller current driving capability than the transistors 109 and 110. Therefore, the channel width (W) of the transistor 108 (or
The ratio of the channel width to the channel length (L) (W / L)) is larger than the channel width (W) of the transistor 109 and the transistor 110 (or the ratio of the channel width to the channel length (L) (W / L)). Can be small.

One embodiment of the semiconductor device of the present invention can have a structure including a plurality of stages 10 illustrated in FIGS. For example, as illustrated in FIG. 3, the semiconductor device 100 includes a plurality of stages 10.
A configuration in which the input terminal IN is connected to the preceding output terminal OUT and the inverting input terminal INB is connected to the preceding inverting output terminal OUTB in a cascade connection (cascade connection) may be employed. Here, the logical value of the signal input to the terminal C1 can be made different in the adjacent stages of the plurality of stages 10 (that is, in the adjacent stage of the plurality of stages 10, the terminal C2
The logic value of the signal input to can be different). For example, in a certain stage 10,
A clock signal is input to the terminal C1, and a clock inversion signal is input to the terminal C2.
In the stage 10 adjacent to 0, a clock inversion signal can be input to the terminal C1 and a clock signal can be input to the terminal C2. In FIG. 3, the clock signal is indicated by CLK, and its inverted signal is indicated by CLKB. In addition, inverted signals can be input to the input terminal IN and the inverting input terminal INB of the first stage among the plurality of stages 10 connected in cascade. In FIG. 3, the signal SP is input to the input terminal IN of the first stage, and the inverted input terminal INB
Is inputted with an inverted signal SPB of the signal SP.

The semiconductor device 100 illustrated in FIG. 3 has a function of sequentially holding the signal input to the input terminal IN of the first stage in each stage 10 in synchronization with the clock signal. Therefore, the semiconductor device 100 can also be referred to as a shift register. The signal SP can also be called a start pulse. The semiconductor device 100 sequentially shifts the start pulse in synchronization with the clock signal CLK, and outputs the output SR1.
, SR2, SR3, and so on. The semiconductor device 100 has outputs SR1, S
The load can be driven by R2 and SR3. Outputs SR1, SR2, SR
3 is an output signal from the output terminal OUT of each stage 10, but is not limited thereto. For example, output signals from the inverting output terminal OUTB of each stage 10 may be used as the outputs SR1, SR2, SR3. Furthermore, only the outputs SR2, SR4, SR6 of the even-numbered stage 10 may be used as the output of the semiconductor device 100 to drive the load.

In the semiconductor device described in this embodiment, the switches (switch SW1, switch SW1
2, a switch SW3, a switch SW4), and a logic circuit (a logic circuit INV1, a logic circuit INV2, a logic circuit INV3, and a logic circuit INV4) in which an input signal is input to the input terminal through the switch that is in a conductive state. Amplifier circuit (amplifier circuit BUF1 and amplifier circuit BUF2)
In the switch, the conductive state or the non-conductive state is selected by a clock signal (or its inverted signal). On the other hand, the amplifier circuit outputs a signal having the same logical value as the input signal from the output terminal OUT by selecting the connection between the high power supply line and the output terminal and the connection between the low power supply line and the output terminal. The output of the amplifier circuit is used as the output of the semiconductor device. Thus, the load driven by the semiconductor device is driven by being connected to the high power line or the low power line.
With such a configuration, the semiconductor device does not drive the load using the high-level potential (or low-level potential) of the clock signal, so that the clock signal generation circuit does not require a large current driving capability. Therefore, the circuit area of the clock signal generation circuit can be reduced.

In addition, when all the transistors included in the semiconductor device have the same conductivity type, the manufacturing process of the semiconductor device can be simplified. Thus, the yield can be improved and the cost can be reduced. In this case, an amplifier circuit (amplifier circuit BUF1 and amplifier circuit BUF2
) Is configured to correct the output signal using a bootstrap circuit. In this way, even in an amplifier circuit configured using unipolar transistors, an output signal having an amplitude voltage (roughly) equal to the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential) can be obtained.

Furthermore, the logic circuit has a plurality of input terminals (an input terminal to which an input signal is input and an inverting input terminal to which a signal obtained by inverting the logic value of the input signal is input), and a high power line and a low power line By controlling the connection between one of the output terminal and the output terminal by a signal input to the inverting input terminal, and controlling the connection between the other of the high power line and the low power line and the output terminal by a signal input to the input terminal, The logic value of the input signal input to the input terminal can be inverted and output from the output terminal. Thus, even in a logic circuit configured using unipolar transistors, a transistor provided between the high power supply line and the output terminal, and a transistor provided between the low power supply line and the output terminal. When one of the two is on, the other can be off. Therefore, a through current in a circuit provided between the high power line and the low power line can be suppressed.

The amplifier circuit has a plurality of input terminals (an input terminal to which an input signal is input and an inverting input terminal to which a signal obtained by inverting the logical value of the input signal is input), and one of the high power line and the low power line The input terminal is controlled by a signal input to the inverting input terminal, and the connection between the other of the high power line and the low power line and the output terminal is controlled by a signal input to the input terminal. A signal having the same logical value as that of the input signal input to the output terminal can be output from the output terminal. Thus, even in an amplifier circuit configured using a unipolar transistor, a transistor provided between the high power supply line and the output terminal, and a transistor provided between the low power supply line and the output terminal. When one of the two is on, the other can be off. Therefore, a through current in a circuit provided between the high power line and the low power line can be suppressed.

In addition, a transistor included in the semiconductor device includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes includes the semiconductor layer and the first gate. The insulating layer can overlap with each other, and the other of the pair of gate electrodes can overlap with the semiconductor layer and the second gate insulating layer. The other of the pair of gate electrodes (back gate) can be connected to the source of the transistor. Alternatively, in the case where the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) can be connected to the low power supply line. In the case where the transistor is a p-channel transistor, the other of the pair of gate electrodes (back gate) can be connected to a high power supply line. Thus, each transistor can be prevented from being normally on. Therefore, malfunction of the semiconductor device can be suppressed and a through current can also be suppressed.

This embodiment can be implemented freely combining with any of the other embodiments.

(Embodiment 3)
In this embodiment, a specific embodiment of a semiconductor device of the present invention will be described with reference to FIGS.

The semiconductor device can have a structure having a stage 10 shown in FIG. The stage 10 includes an input terminal IN, an inverting input terminal INB, a switch SW1, a switch SW2, and a switch SW3.
A switch SW4, a logic circuit INV1, a logic circuit INV2, a logic circuit INV3, a logic circuit INV4, an amplifier circuit BUF1, an amplifier circuit BUF2, an amplifier circuit BUF3, an amplifier circuit BUF4, and an output terminal OUT. And an inverting output terminal OUTB.

The logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 each have an input terminal IN, an inverting input terminal INB, and an output terminal OUT, and invert the signal input to the input terminal IN. Output from the output terminal OUT. The logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 can also be referred to as inverter circuits. The amplifier circuit BUF1, the amplifier circuit BUF2, the amplifier circuit BUF3, and the amplifier circuit BUF4 each have an input terminal IN, an inverting input terminal INB, and an output terminal OUT.
Impedance conversion of the signal input to N (lower impedance) and output terminal OUT
Output from. The output terminal OUT of the logic circuit INV1 is the input terminal IN of the amplifier circuit BUF1.
And the inverting input terminal INB of the amplifier circuit BUF2. The output terminal OUT of the logic circuit INV2 is connected to the inverting input terminal INB of the amplifier circuit BUF1 and the input terminal IN of the amplifier circuit BUF2. The output terminal OUT of the amplifier circuit BUF1 is connected to the input terminal IN of the logic circuit INV3, the inverting input terminal INB of the logic circuit INV4, and the output terminal OUT. The output terminal OUT of the amplifier circuit BUF2 is connected to the inverting input terminal INB of the logic circuit INV3 and the logic circuit I.
It is connected to the input terminal IN and the inverted output terminal OUTB of NV4. The output terminal OUT of the logic circuit INV3 is connected to the input terminal IN of the amplifier circuit BUF3 and the inverting input terminal INB of the amplifier circuit BUF4. The output terminal OUT of the logic circuit INV4 is connected to the inverting input terminal INB of the amplifier circuit BUF3 and the input terminal IN of the amplifier circuit BUF4. Switch SW1,
Each of the switch SW2, the switch SW3, and the switch SW4 has a function of selecting a conduction state or a non-conduction state between the terminal A and the terminal B by a signal input to the terminal X.
Thus, the switch SW1 selects a conduction state or non-conduction state between the input terminal IN and the input terminal IN of the logic circuit INV1 and the inverting input terminal INB of the logic circuit INV2 according to a signal input to the terminal X. Have The switch SW2 has an inverting input terminal INB,
It has a function of selecting a conduction state or non-conduction state between the inverting input terminal INB of the logic circuit INV1 and the input terminal IN of the logic circuit INV2 by a signal input to the terminal X. The terminals X of the switches SW1 and SW2 are connected to the terminal C1, and one of the clock signal and its inverted signal is input to the terminal C1. The switch SW3 includes an output terminal OUT of the amplifier circuit BUF3, an input terminal IN of the logic circuit INV1, and an inverting input terminal IN of the logic circuit INV2.
A function of selecting a conduction state or a non-conduction state between the terminal B and the terminal B according to a signal input to the terminal X. The switch SW4 selects a conduction state or non-conduction state between the output terminal OUT of the amplifier circuit BUF4 and the inverting input terminal INB of the logic circuit INV1 and the input terminal IN of the logic circuit INV2 according to a signal input to the terminal X It has the function to do. The terminals X of the switches SW3 and SW4 are connected to the terminal C2, and the other of the clock signal and its inverted signal is input to the terminal C2.

In the stage 10 shown in FIG. 6, the switch SW1 is generated by the clock signal (or its inverted signal).
When the switch SW2 is conductive, the inverted signal of the clock signal (or the clock signal)
Thus, the switch SW3 and the switch SW4 are turned off, and when the switch SW1 and the switch SW2 are turned off by the clock signal (or its inverted signal), the switch SW3 and the switch SW4 are turned on by the inverted signal (or clock signal) of the clock signal. It becomes a conductive state. Therefore, it has a function of holding a signal input to the input terminal IN in synchronization with the clock signal. Therefore, the stage 10 illustrated in FIG. 6 can also be called a flip-flop circuit or a latch circuit.

One mode of more specific configurations of the amplifier circuit BUF1, the amplifier circuit BUF2, the amplifier circuit BUF3, and the amplifier circuit BUF4 can be the same as the amplifier circuit BUF shown in FIG. 5 in the second embodiment. Description is omitted.

Note that in FIG. 6, each of the logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 can have a structure similar to that of the logic circuit INV illustrated in FIG. As described in Embodiment 1, the circuit configuration of the logic circuit INV illustrated in FIG. 2B can be simplified as compared with the logic circuit INV illustrated in FIG. Voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, | V1-V2
It is impossible to output an output signal having a predetermined amplitude equal to |

However, in FIG. 6, the outputs of the logic circuit INV1 and the logic circuit INV2 are connected to the amplifier circuit BU.
F1 and amplification circuit BUF2 amplify the output terminal OUT and inverted output terminal O of each stage.
This is an output signal from the UTB. Further, the output of the logic circuit INV3 and the output of the logic circuit INV4 are amplified by the amplifier circuit BUF3 and the amplifier circuit BUF4. Therefore, the logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 have an amplitude (approximately) equal to the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, | V1−V2 |). Even if the output signal cannot be output, the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential, ie, | V1-V2 |
Output signal having the same amplitude as (approx.). Thus, a semiconductor device capable of outputting a signal having a predetermined amplitude is obtained.

In particular, in the configuration shown in FIG. 6, the logic circuit IN is connected via the switches SW3 and SW4.
Signals input to V1 and the logic circuit INV2 are also supplied to the amplifier circuit BUF3 and the amplifier circuit BUF4.
Thus, a signal having an amplitude substantially equivalent to the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential, that is, corresponding to | V1−V2 |) is obtained. Therefore, the logic circuit INV1 and the logic circuit IN
Even if the threshold voltage of the transistors constituting V2 varies somewhat due to deterioration over time or the like, malfunctions of these logic circuits can be suppressed.

Note that any or all of the logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 in FIG. 6 are the same as the logic circuit I illustrated in FIG.
A configuration similar to that of NV is also possible.

Further, each of the switch SW1 and the switch SW2 is shown in FIG.
Since it can be set as the structure similar to shown by, description is abbreviate | omitted. Each of the switch SW3 and the switch SW4 can have a structure similar to that illustrated in FIG. 2D in Embodiment 1, and thus description thereof is omitted.

Here, since the switch may have a smaller current driving capability than the logic circuit or the amplifier circuit, the size of the transistor constituting the switch can be made smaller than the size of the transistor constituting the logic circuit or the amplifier circuit. That is, the transistor 106 and the transistor 1
07 channel width (W) (or ratio of channel width to channel length (L) (W / L)
) Is the transistor 104, transistor 105, transistor 108, transistor 1
09 and the transistor 110 can be smaller than the channel width (W) (or the ratio of the channel width to the channel length (L) (W / L)). Thus, high definition and small size of the semiconductor device can be achieved.

Since the logic circuit INV1, the logic circuit INV2, the logic circuit INV3, and the logic circuit INV4 do not directly drive the load connected to the output terminal OUT, the amplifier circuit BUF1 and the amplifier circuit B
The current driving capability may be smaller than that of UF2. Therefore, the logic circuit INV1, the logic circuit I
The channel width (W) (or the ratio of the channel width to the channel length (L) (W / L)) of the transistors (transistors 104 and 105) included in the NV2, the logic circuit INV3, and the logic circuit INV4 is an amplifier circuit. Channel width (W) (or ratio of channel width to channel length (L) (W / L) of transistors (transistor 108, transistor 109, and transistor 110, in particular transistor 109 and transistor 110) included in BUF1 and amplifier circuit BUF2 ). Thus,
High definition and miniaturization of a semiconductor device can be achieved.

In the amplifier circuit BUF illustrated in FIG. 5, the transistor 108 does not directly drive a load connected to the output terminal OUT, and thus may have a smaller current driving capability than the transistors 109 and 110. Therefore, the channel width (W) of the transistor 108 (or
The ratio of the channel width to the channel length (L) (W / L)) is larger than the channel width (W) of the transistor 109 and the transistor 110 (or the ratio of the channel width to the channel length (L) (W / L)). Can be small.

Since the amplifier circuit BUF3 and the amplifier circuit BUF4 do not directly drive the load connected to the output terminal OUT, the current drive capability may be smaller than that of the amplifier circuit BUF1 and the amplifier circuit BUF2. Therefore, the channel width (W) (or the ratio of the channel width to the channel length (L) of the transistors (transistors 108, 109, and 110, in particular, the transistors 109 and 110) included in the amplifier circuits BUF3 and BUF4 ( W / L)) corresponds to the channel width (W) (or channel length (L)) of the transistors (transistor 108, transistor 109 and transistor 110, in particular transistor 109 and transistor 110) included in the amplifier circuit BUF1 and the amplifier circuit BUF2. The channel width ratio (W / L) can be made smaller. Thus, high definition and small size of the semiconductor device can be achieved.

One embodiment of the semiconductor device of the present invention can have a structure including a plurality of stages 10 illustrated in FIGS. For example, as illustrated in FIG. 3, the semiconductor device 100 includes a plurality of stages 10.
A configuration in which the input terminal IN is connected to the preceding output terminal OUT and the inverting input terminal INB is connected to the preceding inverting output terminal OUTB in a cascade connection (cascade connection) may be employed. Here, the logical value of the signal input to the terminal C1 can be made different in the adjacent stages of the plurality of stages 10 (that is, in the adjacent stage of the plurality of stages 10, the terminal C2
The logic value of the signal input to can be different). For example, in a certain stage 10,
A clock signal is input to the terminal C1, and a clock inversion signal is input to the terminal C2.
In the stage 10 adjacent to 0, a clock inversion signal can be input to the terminal C1 and a clock signal can be input to the terminal C2. In FIG. 3, the clock signal is indicated by CLK, and its inverted signal is indicated by CLKB. In addition, inverted signals can be input to the input terminal IN and the inverting input terminal INB of the first stage among the plurality of stages 10 connected in cascade. In FIG. 3, the signal SP is input to the input terminal IN of the first stage, and the inverted input terminal INB
Is inputted with an inverted signal SPB of the signal SP.

The semiconductor device 100 illustrated in FIG. 3 has a function of sequentially holding the signal input to the input terminal IN of the first stage in each stage 10 in synchronization with the clock signal. Therefore, the semiconductor device 100 can also be referred to as a shift register. The signal SP can also be called a start pulse. The semiconductor device 100 sequentially shifts the start pulse in synchronization with the clock signal CLK, and outputs the output SR1.
, SR2, SR3, and so on. The semiconductor device 100 has outputs SR1, S
The load can be driven by R2 and SR3. Outputs SR1, SR2, SR
3 is an output signal from the output terminal OUT of each stage 10, but is not limited thereto. For example, output signals from the inverting output terminal OUTB of each stage 10 may be used as the outputs SR1, SR2, SR3. Furthermore, only the outputs SR2, SR4, SR6 of the even-numbered stage 10 may be used as the output of the semiconductor device 100 to drive the load.

In the semiconductor device described in this embodiment, the switches (switch SW1, switch SW1
2, a switch SW3, a switch SW4), and a logic circuit (a logic circuit INV1, a logic circuit INV2, a logic circuit INV3, and a logic circuit INV4) in which an input signal is input to the input terminal through the switch that is in a conductive state. The switch has an amplifier circuit (amplifier circuit BUF1, amplifier circuit BUF2, amplifier circuit BUF3, and amplifier circuit BUF4), and the switch is selected to be conductive or non-conductive by a clock signal (or its inverted signal). On the other hand, the amplification circuit selects the connection between the high power supply line and the output terminal and the connection between the low power supply line and the output terminal.
A signal having the same logical value as the input signal is output from the output terminal OUT. The output of the amplifier circuit is used as the output of the semiconductor device. Thus, the load driven by the semiconductor device is driven by being connected to the high power line or the low power line. With such a configuration, the semiconductor device does not drive the load using the high-level potential (or low-level potential) of the clock signal, so that the clock signal generation circuit does not require a large current driving capability. Therefore, the circuit area of the clock signal generation circuit can be reduced.

In addition, when all the transistors included in the semiconductor device have the same conductivity type, the manufacturing process of the semiconductor device can be simplified. Thus, the yield can be improved and the cost can be reduced. In this case, an amplifier circuit (amplifier circuit BUF1, amplifier circuit BUF2,
The amplifier circuit BUF3 and the amplifier circuit BUF4) are configured to correct the output signal using a bootstrap circuit. In this way, even in an amplifier circuit configured using unipolar transistors, an output signal having an amplitude voltage (roughly) equal to the power supply voltage (corresponding to the difference between the high power supply potential and the low power supply potential) can be obtained.

Furthermore, the logic circuit has a plurality of input terminals (an input terminal to which an input signal is input and an inverting input terminal to which a signal obtained by inverting the logic value of the input signal is input), and a high power line and a low power line By controlling the connection between one of the output terminal and the output terminal by a signal input to the inverting input terminal, and controlling the connection between the other of the high power line and the low power line and the output terminal by a signal input to the input terminal, The logic value of the input signal input to the input terminal can be inverted and output from the output terminal. Thus, even in a logic circuit configured using unipolar transistors, a transistor provided between the high power supply line and the output terminal, and a transistor provided between the low power supply line and the output terminal. When one of the two is on, the other can be off. Therefore, a through current in a circuit provided between the high power line and the low power line can be suppressed.

The amplifier circuit has a plurality of input terminals (an input terminal to which an input signal is input and an inverting input terminal to which a signal obtained by inverting the logical value of the input signal is input), and one of the high power line and the low power line The input terminal is controlled by a signal input to the inverting input terminal, and the connection between the other of the high power line and the low power line and the output terminal is controlled by a signal input to the input terminal. A signal having the same logical value as that of the input signal input to the output terminal can be output from the output terminal. Thus, even in an amplifier circuit configured using a unipolar transistor, a transistor provided between the high power supply line and the output terminal, and a transistor provided between the low power supply line and the output terminal. When one of the two is on, the other can be off. Therefore, a through current in a circuit provided between the high power line and the low power line can be suppressed.

In addition, a transistor included in the semiconductor device includes a semiconductor layer in which a channel is formed and a pair of gate electrodes provided with the semiconductor layer interposed therebetween, and one of the pair of gate electrodes includes the semiconductor layer and the first gate. The insulating layer can overlap with each other, and the other of the pair of gate electrodes can overlap with the semiconductor layer and the second gate insulating layer. The other of the pair of gate electrodes (back gate) can be connected to the source of the transistor. Alternatively, in the case where the transistor is an n-channel transistor, the other of the pair of gate electrodes (back gate) can be connected to the low power supply line. In the case where the transistor is a p-channel transistor, the other of the pair of gate electrodes (back gate) can be connected to a high power supply line. Thus, each transistor can be prevented from being normally on. Therefore, malfunction of the semiconductor device can be suppressed and a through current can also be suppressed.

This embodiment can be implemented freely combining with any of the other embodiments.

(Embodiment 4)
In this embodiment mode, transistors included in the semiconductor device described in the above embodiment mode (
For example, one embodiment of a structure of the transistor 101, the transistor 102, the transistor 103, the transistor 104, the transistor 105, the transistor 106, the transistor 107, the transistor 108, the transistor 109, and the transistor 110) is described with reference to FIGS.

8A shows a top view of the transistor, and FIG. 8B shows an A in FIG. 8A.
The example of sectional drawing of 1-A2 is shown. 8 uses a layer including an oxide semiconductor (hereinafter referred to as an oxide semiconductor layer) as a semiconductor layer in which a channel is formed.
An advantage of using an oxide semiconductor layer is that high mobility and low off-state current can be realized by a simple process and a low-temperature process.

As shown in FIG. 8B, the transistor 410 includes a gate electrode 402, a gate insulating layer 404, an oxide semiconductor layer 412, a drain electrode 414a, and the like over a substrate 400 having an insulating surface.
And a source electrode 414b. The gate insulating layer 41 in contact with the oxide semiconductor layer 412 is also provided.
6, and a gate electrode 418 is further provided over the gate insulating layer 416. Note that one of the gate electrode 402 and the gate electrode 418 corresponds to a gate in the above embodiment, and the other of the gate electrode 402 and the gate electrode 418 corresponds to a back gate in the above embodiment. The source electrode 414b corresponds to the source in the previous embodiment, and the drain electrode 414a corresponds to the drain in the previous embodiment.

Note that in some of the plurality of transistors included in the semiconductor device, one of the gate electrode 402 and the gate electrode 418 is used as a gate, and the other of the gate electrode 402 and the gate electrode 418 is used as a back gate. Among the transistors, the other transistor has one of the gate electrode 402 and the gate electrode 418 as a back gate, and the gate electrode 40
2 and the other of the gate electrode 418 may be a gate. That is, the positional relationship between the “gate” and the “back gate” can be reversed in some of the plurality of transistors included in the semiconductor device and the other transistors. For example, some of the plurality of transistors included in the semiconductor device are bottom-gate transistors having a gate electrode 402 provided below the oxide semiconductor layer 412 as a gate. Among the plurality of transistors included in the semiconductor device, Another transistor can be a top-gate transistor in which a gate electrode 418 provided above the oxide semiconductor layer 412 is used as a gate. The back gate (which becomes the gate electrode 402 or the gate electrode 418 depending on the transistor) can be electrically connected to the source of the transistor. Alternatively, when the transistor is an n-channel transistor, the back gate can be electrically connected to the low power supply line. In the case where the transistor is a p-channel transistor, the back gate can be electrically connected to the high power supply line.

In this embodiment, the oxide semiconductor layer 412 is used as the semiconductor layer. Oxide semiconductor layer 41
The transistor 410 using 2 can have extremely low off-state current. Therefore, by using this for a shift register or the like, the potential of each node in the circuit can be easily held, and the probability of malfunction can be suppressed extremely low.

In the transistor 410, the other of the gate electrode 402 and the gate electrode 418 (back gate) can be connected to the source electrode 414b. Note that in the case where the transistor 410 is an n-channel transistor, the source electrode 414b may be connected to a low power supply line.
Thus, the transistor 410 can be prevented from being normally on. Also,
The gate electrode 402 and the gate electrode 418 may be connected to serve as the gate of the transistor 410.

A transistor 410 illustrated in FIG. 8 has a structure in which a drain electrode 414a and a source electrode 414b partially overlap with a gate electrode 402.
4b and the gate electrode 402 may not be overlapped.

There is no particular limitation on the crystallinity of the oxide semiconductor layer 412. For example, the oxide semiconductor layer 412 can be non-single crystal and can be amorphous or polycrystalline. Moreover, the structure which contains the part which has crystallinity in an amorphous may be sufficient.

Since an oxide semiconductor layer in an amorphous state can obtain a flat surface relatively easily, interface scattering can be reduced by manufacturing a transistor using the oxide semiconductor layer.
A relatively high mobility can be obtained.

Further, defects in the bulk can be reduced more in an oxide semiconductor layer having crystallinity.
When the planarity of the surface of the oxide semiconductor layer 412 having crystallinity is increased, higher mobility than that of an oxide semiconductor layer in an amorphous state can be obtained. In order to improve the flatness of the surface, it is preferable to form an oxide semiconductor on the flat surface. Specifically, the average surface roughness (
Ra) may be formed on the surface of 1 nm or less, preferably 0.3 nm or less, more preferably 0.1 nm or less.

Ra is an arithmetic mean roughness defined in JIS B0601: 2001 (ISO4287: 1997) expanded to three dimensions so that it can be applied to curved surfaces. It can be expressed as “average value of absolute values” and is defined by the following equation.

Here, the designated surface is a surface to be subjected to roughness measurement, and the coordinates ((x1, y1, f (x1,
y1)), (x1, y2, f (x1, y2)), (x2, y1, f (x2, y1)), (
A rectangular area represented by four points x2, y2, and f (x2, y2)), the rectangular area obtained by projecting the designated surface onto the xy plane is S0, and the height of the reference surface (the average height of the designated surface) ) Is Z0. R
a can be measured with an atomic force microscope (AFM).

As the oxide semiconductor layer 412, a CAAC-OS (C Axis Aligned Cry) is used.
A stalled oxide semiconductor) film can be used.

The CAAC-OS film is not completely single crystal nor completely amorphous. The CAAC-OS film is an oxide semiconductor film with a crystal-amorphous mixed phase structure where crystal parts are included in an amorphous phase. Note that the crystal part is often large enough to fit in a cube whose one side is less than 100 nm. Also,
Transmission Electron Microscope (TEM: Transmission Electron Micro)
In the observation image by (scope), the boundary between the amorphous part and the crystal part included in the CAAC-OS film is not clear. Further, a grain boundary (also referred to as a grain boundary) cannot be confirmed in the CAAC-OS film by TEM. Therefore, in the CAAC-OS film, reduction in electron mobility due to grain boundaries is suppressed.

In the crystal part included in the CAAC-OS film, the c-axis is aligned in a direction parallel to the normal vector of the formation surface of the CAAC-OS film or the normal vector of the surface, and triangular when viewed from the direction perpendicular to the ab plane. It has a shape or hexagonal atomic arrangement, and metal atoms are arranged in layers or metal atoms and oxygen atoms are arranged in layers as viewed from the direction perpendicular to the c-axis. Note that the directions of the a-axis and the b-axis may be different between different crystal parts. In the present specification, when simply described as vertical, 8
The range of 5 ° to 95 ° is also included. In addition, when simply described as parallel, −5
A range of not less than 5 ° and not more than 5 ° is also included.

Note that the distribution of crystal parts in the CAAC-OS film is not necessarily uniform. For example, CAA
In the formation process of the C-OS film, when crystal growth is performed from the surface side of the oxide semiconductor film, the ratio of crystal parts in the vicinity of the surface of the oxide semiconductor film may be higher in the vicinity of the surface. CA
When an impurity is added to the AC-OS film, the crystal part in a region to which the impurity is added becomes amorphous in some cases.

Since the c-axis of the crystal part included in the CAAC-OS film is aligned in a direction parallel to the normal vector of the formation surface of the CAAC-OS film or the normal vector of the surface, the shape of the CAAC-OS film (formation surface) Depending on the cross-sectional shape of the surface or the cross-sectional shape of the surface). Note that the c-axis direction of the crystal part is a normal vector of a surface where the CAAC-OS film is formed or a vector parallel to the normal direction of the surface. The crystal part is formed by film formation or by performing crystallization treatment such as heat treatment after film formation.

A transistor including a CAAC-OS film can reduce variation in electrical characteristics due to irradiation with visible light or ultraviolet light. Therefore, the transistor has high reliability.

Note that part of oxygen included in the oxide semiconductor film may be replaced with nitrogen.

There are three methods for obtaining a CAAC-OS film. First, the film formation temperature is 200 ° C.
This is a method in which an oxide semiconductor layer is formed at a temperature of 500 ° C. or lower and is c-axis oriented substantially perpendicular to the surface. The second is a method of forming a thin film and then performing a heat treatment at 200 ° C. or more and 700 ° C. or less so as to make the c-axis orientation substantially perpendicular to the surface. The third is a method of forming a thin film of the first layer, then performing a heat treatment at 200 ° C. or more and 700 ° C. or less, forming a second layer, and aligning the c-axis substantially perpendicularly to the surface. .

The thickness of the oxide semiconductor layer 412 is 1 nm to 30 nm (preferably 5 nm to 10 n).
m or less), sputtering method, MBE (Molecular Beam Epita)
xy) method, CVD method, pulsed laser deposition method, ALD (Atomic Layer Dep)
osition) method or the like can be used as appropriate. The oxide semiconductor layer 412 may be formed using a sputtering apparatus which performs film formation in a state where a plurality of substrate surfaces are set substantially perpendicular to the surface of the sputtering target.

The oxide semiconductor layer 412 used for the semiconductor layer in this embodiment is preferably highly purified so that hydrogen which is an n-type impurity is removed from the oxide semiconductor and impurities other than the main component are not included as much as possible.

Note that the number of carriers in the highly purified oxide semiconductor layer is extremely small, and the carrier density is 1
× 10 ¹⁴ / cm ^{3 or} less, preferably less than 1 × 10 ¹² / cm ³ , more preferably 1 ×
It becomes less than 10 ¹¹ / cm ³ . In addition, since the number of carriers is small in this manner, the current in the off state (off current) is sufficiently small.

Specifically, in a transistor including the above-described oxide semiconductor layer, an off-current density corresponding to a value obtained by dividing off-state current at room temperature (25 ° C.) by the channel width of the transistor has a channel length L of 10 μm, 100 zA / μm (1 × 10 ⁻¹⁹ A / μm) or less, and further 10 zA / μ under the condition that the voltage between the source and drain of the transistor is 3V
m (1 × 10 ⁻²⁰ A / μm) or less.

In addition, in the transistor 410 including the highly purified oxide semiconductor layer, the temperature dependence of the on-state current is hardly observed, and the off-state current remains very small.

Next, a manufacturing process of the transistor 410 illustrated in FIGS. 8A to 8C will be described with reference to FIGS.

First, after a conductive film is formed over the substrate 400 having an insulating surface, the gate electrode 402 is formed by a photolithography process. Note that the resist mask used in the photolithography step may be formed by an inkjet method. When the resist mask is formed by an ink-jet method, a manufacturing cost can be reduced because a photomask is not used.

There is no particular limitation on a substrate that can be used as the substrate 400 having an insulating surface as long as it has heat resistance enough to withstand heat treatment performed later. For example, glass substrates such as barium borosilicate glass and alumino borosilicate glass, ceramic substrates,
A quartz substrate, a sapphire substrate, or the like can be used. In addition, a single crystal semiconductor substrate such as silicon or silicon carbide, a polycrystalline semiconductor substrate, a compound semiconductor substrate such as silicon germanium, an SOI substrate, or the like can be applied, and a semiconductor element provided on these substrates, The substrate 400 may be used.

Alternatively, a semiconductor device may be manufactured using a flexible substrate as the substrate 400. In order to manufacture a flexible semiconductor device, the transistor 410 including the oxide semiconductor layer 412 may be formed directly over a flexible substrate, or the transistor including the oxide semiconductor layer 412 over another manufacturing substrate. 410 may be manufactured and then peeled off and transferred to a flexible substrate. Note that in order to separate the transistor from the manufacturing substrate and transfer it to the flexible substrate, a separation layer may be provided between the manufacturing substrate and the transistor 410 including the oxide semiconductor layer 412.

As a material for the gate electrode 402, a metal material such as molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, or scandium, or an alloy material containing any of these materials as its main component can be used. As the gate electrode 402, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus, or a silicide film such as nickel silicide may be used. The gate electrode 402 may have a single-layer structure or a stacked structure.

As a material of the gate electrode 402, indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc A conductive material such as oxide or indium tin oxide to which silicon oxide is added can also be used. Alternatively, a stacked structure of the conductive material and the metal material can be employed.

Note that as one layer of the gate electrode 402 which is in contact with the gate insulating layer 404 to be formed later, a metal oxide film containing nitrogen, specifically, an In—Ga—Zn—O film containing nitrogen or an I containing nitrogen is used.
n-Sn-O film, In-Ga-O film containing nitrogen, In-Zn-O film containing nitrogen, Sn-O film containing nitrogen, In-O film containing nitrogen, metal nitriding A film (InN, SnN, etc.) can be used. These films have a work function of 5 eV (electron volt), preferably 5.5 eV (electron volt) or more, and when used as a gate electrode, the threshold voltage of an n-channel transistor can be positive. A normally-off switching element can be realized.

Next, the gate insulating layer 404 is formed over the gate electrode 402.

The thickness of the gate insulating layer 404 is 1 nm or more and 20 nm or less.
A method, a CVD method, a pulse laser deposition method, an ALD method, or the like can be used as appropriate. Alternatively, the gate insulating layer 404 may be formed using a sputtering apparatus which performs film formation in a state where a plurality of substrate surfaces are set substantially perpendicular to the sputtering target surface.

As a material of the gate insulating layer 404, a silicon oxide film, a gallium oxide film, an aluminum oxide film, a silicon nitride film, a silicon oxynitride film, an aluminum oxynitride film, or a silicon nitride oxide film can be used. The gate insulating layer 404 preferably contains oxygen in a portion in contact with the oxide semiconductor layer 406 to be formed later. In particular, the gate insulating layer 404 preferably includes oxygen in the film (in the bulk) in an amount exceeding at least the stoichiometric ratio. For example, when a silicon oxide film is used as the gate insulating layer 404, SiO 2 is used. _{2 + α}
(Where α> 0). In this embodiment, as the gate insulating layer 404, SiO _2+
A silicon oxide film with _α (where α> 0) is used. By using this silicon oxide film as the gate insulating layer 404, oxygen can be supplied to the oxide semiconductor layer 406 to be formed later. Further, the gate insulating layer 404 is preferably formed in consideration of the size of a transistor to be manufactured and the step coverage of the gate insulating layer 404.

In addition, as a material of the gate insulating layer 404, hafnium oxide, yttrium oxide, hafnium silicate (HfSi _x O _y , (x> 0, y> 0)), nitrogen-added hafnium silicate (HfSiO _x N _y (x> 0) Y> 0)), hafnium aluminate (HfAl _x
The gate leakage current can be reduced by using a high-k material such as O _y (x> 0, y> 0)) or lanthanum oxide. Further, the gate insulating layer 404 may have a single-layer structure or a stacked structure.

Next, the oxide semiconductor layer 406 is formed over the gate insulating layer 404 (see FIG. 9A).

Here, in the formation process of the oxide semiconductor layer 406, in order to prevent the oxide semiconductor layer from containing hydrogen or water as much as possible, as a pretreatment for the formation of the oxide semiconductor layer 406, a preparatory process for a sputtering apparatus is performed. It is preferable that the substrate over which the gate insulating layer 404 is formed be preheated in a heating chamber so that impurities such as hydrogen and moisture adsorbed on the substrate 400 and the gate insulating layer 404 are desorbed and exhausted. Note that a cryopump is preferable as an exhaustion unit provided in the preheating chamber.

Planarization treatment may be performed on a region of the gate insulating layer 404 which is in contact with the oxide semiconductor layer 406. The planarization process is not particularly limited, but is a dry etching process,
Plasma treatment or polishing treatment (for example, chemical mechanical polishing (Chemical Mechanical)
(Nick Polishing: CMP) method) can be used.

As the plasma treatment, for example, reverse sputtering in which an argon gas is introduced to generate plasma can be performed. Reverse sputtering is RF on the substrate side in an argon atmosphere.
In this method, a voltage is applied using a power source to form plasma in the vicinity of the substrate to modify the surface.
Note that nitrogen, helium, oxygen, or the like may be used instead of the argon atmosphere. When reverse sputtering is performed, powdery substances (also referred to as particles or dust) attached to the surface of the gate insulating layer 404 can be removed.

As the planarization process, the dry etching process, the plasma process, or the polishing process may be performed a plurality of times, or a combination thereof. Further, in the case of performing the combination, the order of steps is not particularly limited, and may be set as appropriate in accordance with the uneven state of the surface of the gate insulating layer 404.

Note that the oxide semiconductor layer 406 is formed under a condition in which a large amount of oxygen is contained at the time of film formation (for example, film formation is performed by a sputtering method in an atmosphere containing 100% oxygen) and thus a large amount of oxygen is included ( It is preferable that the oxide semiconductor be a film in which a region where the oxygen content is excessive with respect to the stoichiometric composition in the crystalline state is included.

An oxide semiconductor used for the oxide semiconductor layer 406 preferably contains at least indium (In) or zinc (Zn). In particular, In and Zn are preferably included. In addition, it is preferable that gallium (Ga) be included in addition to the stabilizer for reducing variation in electrical characteristics of the transistor including the oxide semiconductor. Moreover, it is preferable to have tin (Sn) as a stabilizer. Moreover, it is preferable to have hafnium (Hf) as a stabilizer. In addition, aluminum (Al
).

In addition, as other stabilizers, lanthanoids such as lanthanum (La), cerium (
Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium ( Tm), ytterbium (Yb), or lutetium (Lu) may be used alone or in combination.

For example, as an oxide semiconductor, indium oxide, tin oxide, zinc oxide, binary metal oxides such as In—Zn oxide, Sn—Zn oxide, Al—Zn oxide, Zn—Mg oxide Oxides, Sn—Mg oxides, In—Mg oxides, In—Ga oxides, In—Ga—Zn oxides (also referred to as IGZO) which are oxides of ternary metals, In— Al-Zn oxide, In-Sn-Zn oxide, Sn-Ga-Zn oxide, Al-Ga-Zn oxide, Sn-Al-Zn oxide, In-Hf-Zn oxide In-La-Zn-based oxide, In-Ce-Zn-based oxide, In-Pr-Zn-based oxide, In-Nd-Zn-based oxide, In-Sm-Zn-based oxide, In-Eu -Zn-based oxide, In-Gd-Zn-based oxide,
In-Tb-Zn-based oxide, In-Dy-Zn-based oxide, In-Ho-Zn-based oxide, I
n-Er-Zn-based oxide, In-Tm-Zn-based oxide, In-Yb-Zn-based oxide, In
-Lu-Zn-based oxide, In-Sn-Ga-Zn-based oxide which is an oxide of a quaternary metal, I
n-Hf-Ga-Zn-based oxide, In-Al-Ga-Zn-based oxide, In-Sn-Al-
A Zn-based oxide, an In-Sn-Hf-Zn-based oxide, or an In-Hf-Al-Zn-based oxide can be used.

Note that here, for example, an In—Ga—Zn-based oxide means an oxide containing In, Ga, and Zn, and there is no limitation on the ratio of In, Ga, and Zn. Moreover, metal elements other than In, Ga, and Zn may be contained.

Note that in this embodiment, as a target for forming the oxide semiconductor layer 406 by a sputtering method, an oxide target of In: Ga: Zn = 3: 1: 2 [atomic percentage] is used as a composition. An In—Ga—Zn-based oxide film (IGZO film) is formed.

The relative density of the target is 90% to 100%, preferably 95% to 99.9.
% Or less. By using a target with high relative density, the formed oxide semiconductor layer 406 can be a dense film.

As a sputtering gas used for forming the oxide semiconductor layer 406, a high-purity gas from which impurities such as hydrogen, water, a hydroxyl group, or hydride are removed is preferably used.

The substrate is held in a film formation chamber held in a reduced pressure state. Then, a sputtering gas from which hydrogen and moisture have been removed is introduced while moisture remaining in the film formation chamber is removed, and the substrate 40 is used using the target.
An oxide semiconductor layer 406 is formed over 0. In order to remove moisture remaining in the deposition chamber, it is preferable to use an adsorption-type vacuum pump such as a cryopump, an ion pump, or a titanium sublimation pump. Further, the exhaust means may be a turbo molecular pump provided with a cold trap. The film formation chamber evacuated using a cryopump is, for example,
Since a compound containing a hydrogen atom such as a hydrogen atom or water (H ₂ O) (more preferably a compound containing a carbon atom) is exhausted, an impurity contained in the oxide semiconductor layer 406 formed in the deposition chamber The concentration of can be reduced.

The gate insulating layer 404 and the oxide semiconductor layer 406 are preferably formed successively without being released to the atmosphere. When the gate insulating layer 404 and the oxide semiconductor layer 406 are successively formed without being exposed to the air, impurities such as hydrogen and moisture can be prevented from being adsorbed to the surface of the gate insulating layer 404.

Next, heat treatment for removing (dehydrating or dehydrogenating) excess hydrogen (including water and a hydroxyl group) included in the oxide semiconductor layer 406 is performed. By performing heat treatment on the oxide semiconductor layer 406, the oxide semiconductor layer 408 from which excess hydrogen is removed can be formed (FIG. 9).
(See (B)). The temperature of the heat treatment is 300 ° C. or higher and 700 ° C. or lower, or lower than the strain point of the substrate. The heat treatment can be performed under reduced pressure or a nitrogen atmosphere. For example, a substrate is introduced into an electric furnace which is one of heat treatment apparatuses, and the oxide semiconductor layer 406 is subjected to 4 in a nitrogen atmosphere.
Heat treatment is performed at 50 ° C. for 1 hour.

Note that the heat treatment apparatus is not limited to an electric furnace, and an apparatus for heating an object to be processed by heat conduction or heat radiation from a heating element such as a resistance heating element may be used. For example, GRTA (Gas R
API (Temperature Annial), LRTA (Lamp Rapid T)
RTA (Rapid Thermal Anne) such as a Herm Anneal) device
al) apparatus can be used. The LRTA apparatus is an apparatus that heats an object to be processed by radiation of light (electromagnetic waves) emitted from a lamp such as a halogen lamp, a metal halide lamp, a xenon arc lamp, a carbon arc lamp, a high pressure sodium lamp, or a high pressure mercury lamp. The GRTA apparatus is an apparatus that performs heat treatment using a high-temperature gas. For hot gases,
An inert gas that does not react with an object to be processed by heat treatment, such as nitrogen or a rare gas such as argon, is used.

For example, as the heat treatment, GRTA may be performed in which the substrate is placed in an inert gas heated to a high temperature of 650 ° C. to 700 ° C., heated for several minutes, and then the substrate is taken out of the inert gas.

Note that in the heat treatment, it is preferable that water, hydrogen, or the like be not contained in nitrogen or a rare gas such as helium, neon, or argon. Alternatively, the purity of nitrogen or a rare gas such as helium, neon, or argon introduced into the heat treatment apparatus is 6N (99.9999%) or more, preferably 7N (99.99999%) or more (that is, the impurity concentration is 1 ppm or less, preferably Is 0.1
ppm or less).

In addition, after heating the oxide semiconductor layer 406 by heat treatment, a dew point of high-purity oxygen gas, high-purity dinitrogen monoxide gas, or ultra-dry air (CRDS (cavity ring-down laser spectroscopy) method) is supplied to the same furnace. Water content when measured using a meter is 20 ppm (-55 ° C in terms of dew point)
In the following, air of preferably 1 ppm or less, more preferably 10 ppb or less may be introduced. It is preferable that water, hydrogen, and the like are not contained in the oxygen gas or the dinitrogen monoxide gas. Alternatively, the purity of the oxygen gas or nitrous oxide introduced into the heat treatment apparatus is 6N or more, preferably 7N or more (that is, the impurity concentration in the oxygen gas or nitrous oxide is 1 ppm or less,
Preferably it is 0.1 ppm or less. By the action of oxygen gas or dinitrogen monoxide gas, oxygen that is a main component material of the oxide semiconductor that is simultaneously reduced by the impurity removal step by dehydration or dehydrogenation treatment can be supplied.

Further, the heat treatment for dehydration or dehydrogenation may be performed a plurality of times or may be combined with other heat treatments.

When heat treatment for dehydration or dehydrogenation is performed in a state where the film-shaped oxide semiconductor layer 406 covers the gate insulating layer 404 before being processed into an island shape as the oxide semiconductor layer 412, gate insulation is performed. This is preferable because oxygen contained in the layer 404 can be prevented from being outwardly diffused by heat treatment.

In addition, oxygen that is a main component material of the oxide semiconductor may be desorbed and reduced at the same time by the dehydration or dehydrogenation treatment. In the oxide semiconductor layer 408, oxygen vacancies exist at locations where oxygen is released, and donor levels that cause a change in electrical characteristics of the transistor are generated due to the oxygen vacancies.

Therefore, oxygen is preferably supplied to the oxide semiconductor layer 408 that has been subjected to dehydration or dehydrogenation treatment. By supplying oxygen to the oxide semiconductor layer 408, oxygen vacancies in the film can be filled.

For example, an oxide insulating layer containing a large amount (excessive) of oxygen serving as an oxygen supply source is formed as the gate insulating layer 40.
4 and provided in contact with the oxide semiconductor layer 408, oxygen can be supplied from the oxide insulating layer to the oxide semiconductor layer 408. In the above structure, oxygen treatment of the oxide semiconductor layer 408 is performed by performing heat treatment in a state where at least part of the oxide semiconductor layer 408 and the oxide insulating layer subjected to heat treatment as dehydration or dehydrogenation treatment are in contact with each other. May be supplied.

The gate insulating layer 404 and the oxide semiconductor layer 40 containing a large amount (excessive) of oxygen serving as an oxygen supply source
8 can be supplied from the gate insulating layer 404 to the oxide semiconductor layer 408, so that oxygen vacancies in the oxide semiconductor layer 408 can be filled.

Next, the oxide semiconductor layer 408 is formed into an island-shaped oxide semiconductor layer 4 by a photolithography process.
12 is formed (see FIG. 9C). Note that the resist mask used in the photolithography step may be formed by an inkjet method. When the resist mask is formed by an ink-jet method, a manufacturing cost can be reduced because a photomask is not used.

Note that the etching of the oxide semiconductor layer 408 may be dry etching or wet etching, or both may be used. For example, as an etchant used for wet etching of the oxide semiconductor layer 408, a mixed solution of phosphoric acid, acetic acid, and nitric acid, or the like can be used. In addition, ITO07N (manufactured by Kanto Chemical Co., Inc.) may be used.

Next, oxygen (including at least one of oxygen radicals, oxygen atoms, and oxygen ions) may be introduced into the oxide semiconductor layer 412 to supply oxygen into the film.

By introducing oxygen into the oxide semiconductor layer 412 and supplying oxygen into the film, the oxide semiconductor layer 412 can be highly purified. A transistor including the highly purified oxide semiconductor layer 412 is electrically stable because variation in electrical characteristics is suppressed.

As a method for introducing oxygen, an ion implantation method, an ion doping method, a plasma immersion ion implantation method, a plasma treatment, or the like can be used.

In the step of introducing oxygen, when oxygen is introduced into the oxide semiconductor layer 412, the oxygen may be introduced directly into the oxide semiconductor layer 412 or after passing through the gate insulating layer 416 which is formed later.
12 may be introduced. In the case of introducing oxygen through the gate insulating layer 416, an ion implantation method, an ion doping method, a plasma immersion ion implantation method, or the like may be used. However, oxygen is directly introduced into the exposed oxide semiconductor layer 412. In that case, plasma treatment or the like can also be used.

The introduction of oxygen into the oxide semiconductor layer may be performed after dehydration or dehydrogenation treatment, and is not particularly limited. Further, oxygen may be introduced into the oxide semiconductor layer subjected to the dehydration or dehydrogenation treatment a plurality of times.

Next, after a conductive film to be the drain electrode 414a and the source electrode 414b (including a wiring formed using the same layer) is formed over the oxide semiconductor layer 412, the drain electrode 414a and the source electrode are formed by a photolithography process. 414b is formed (see FIG. 9D).
.

The conductive film is formed using a material that can withstand heat treatment performed later. Examples of the conductive film used for the drain electrode 414a and the source electrode 414b include Al, Cr, Cu, Ta, Ti, Mo, and W.
A metal film containing an element selected from the above, or a metal nitride film (a titanium nitride film, a molybdenum nitride film, or a tungsten nitride film) containing the above-described element as a component can be used. Al
A refractory metal film such as Ti, Mo, or W or a metal nitride film thereof (titanium nitride film, molybdenum nitride film, tungsten nitride film) is laminated on one or both of the lower side or upper side of the metal film such as Cu or Cu. It is good also as a composition. In addition, the drain electrode 414a and the source electrode 414b
The conductive film used for the step may be formed of a conductive metal oxide. As the conductive metal oxide, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), indium tin oxide (In ₂ O ₃ —SnO ₂ , abbreviated as ITO), oxidation Indium zinc oxide (In ₂ O ₃ —ZnO) or a metal oxide material containing silicon oxide can be used.

Next, the gate insulating layer 416 is formed so as to cover the oxide semiconductor layer 412, the drain electrode 414a, and the source electrode 414b. Note that a material and a deposition method similar to those of the gate insulating layer 404 can be used as a material and a deposition method of the gate insulating layer 416, and thus detailed description thereof is omitted.

Next, after a conductive film to be the gate electrode 418 is formed over the gate insulating layer 416, the gate electrode 418 is formed by a photolithography process (see FIG. 9E). Note that a material and a deposition method similar to those of the gate electrode 402 can be used as a material and a deposition method of the gate electrode 418, and thus detailed description thereof is omitted.

Through the above steps, the transistor 410 is formed (see FIG. 9E).

Note that a protective insulating layer may be further formed over the gate insulating layer 416 and the gate electrode 418. The protective insulating layer prevents intrusion from the outside such as hydrogen and water. As the protective insulating layer, for example, a silicon nitride film, an aluminum nitride film, or the like can be used. There is no particular limitation on the deposition method, but the RF sputtering method is suitable as a deposition method for the protective insulating layer because of its high mass productivity.

Further, a planarization insulating film for reducing surface unevenness due to the transistor may be formed over the protective insulating layer. As the planarization insulating film, an organic material such as polyimide, acrylic, or benzocyclobutene resin can be used. In addition to the above organic materials, low dielectric constant materials (
low-k material) or the like. Note that the planarization insulating film may be formed by stacking a plurality of insulating films formed using these materials.

Note that after the formation of the protective insulating layer or the planarization insulating film, the film is further heated to 100 ° C. or more in the atmosphere at 200 ° C.
The heat treatment may be performed under the conditions of 1 ° C. or lower and 1 hour or longer and 30 hours or shorter.

As described above, a transistor in which a channel is formed in a highly purified oxide semiconductor layer manufactured using this embodiment has a feature of extremely low off-state current. Therefore, the use of this transistor makes it easy to hold the node potential. Therefore, by using this for a shift register or the like, the probability of malfunction can be kept extremely low.

This embodiment can be implemented freely combining with any of the other embodiments.

The semiconductor device according to one embodiment of the present invention can be used for various electronic devices. As an electronic device, for example, a personal computer (for example, a notebook type or a desktop type), an image reproducing apparatus (typically a DVD: Digital Versatile) provided with a recording medium.
A device having a display capable of reproducing a recording medium such as a disc and displaying the image), a mobile phone, a portable game machine, a portable information terminal, an electronic book, a video camera, a digital still camera, a goggle type display (head mounted display) ), Navigation systems, sound reproducing devices (car audio, digital audio player, etc.), copying machines, facsimiles, printers, printer multifunction devices, automatic teller machines (ATMs), and vending machines.

Examples of electronic devices will be described with reference to FIGS. 10A, 10B, and 10C.

10A and 10B illustrate a tablet terminal that can be folded. FIG. 10 (A)
Is an open state, and the tablet terminal includes a housing 9630, a display portion 9631a, a display portion 9631b, a display mode change switch 9034, a power switch 9035, a power saving mode change switch 9036, a fastener 9033, an operation switch 9038, Have

Part of the display portion 9631 a can be a touch panel region 9632 a and data can be input when a displayed operation key 9037 is touched. The display portion 963
In 1a, as an example, a configuration in which half of the area has a display-only function and a configuration in which the other half has a touch panel function is shown, but the configuration is not limited thereto. Display unit 963
All the regions 1a may have a touch panel function. For example, the display unit 96
The entire surface of 31a can be displayed as a keyboard button and used as a touch panel, and the display portion 9631b can be used as a display screen.

Further, in the display portion 9631b, as in the display portion 9631a, part of the display portion 9631b can be a touch panel region 9632b. Further, a keyboard button can be displayed on the display portion 9631b by touching a position where the keyboard display switching button 9539 on the touch panel is displayed with a finger or a stylus.

Touch input can be performed simultaneously on the touch panel region 9632a and the touch panel region 9632b.

A display mode switching switch 9034 can switch the display direction such as vertical display or horizontal display, and can select switching between monochrome display and color display. The power saving mode change-over switch 9036 can optimize the display luminance in accordance with the amount of external light during use detected by an optical sensor built in the tablet terminal. The tablet terminal may include not only an optical sensor but also other detection devices such as a gyroscope, an acceleration sensor, and other sensors that detect inclination.

FIG. 10A illustrates an example in which the display areas of the display portion 9631b and the display portion 9631a are the same, but there is no particular limitation, and one size may be different from the other size, and the display quality may be different. May be different. For example, one display panel may be capable of displaying images with higher definition than the other.

FIG. 10B illustrates a closed state, in which the tablet terminal includes a housing 9630, a solar cell 96
33, a charge / discharge control circuit 9634, a battery 9635, and a DCDC converter 9636. Note that in FIG. 10B, a battery 9635 is illustrated as an example of the charge / discharge control circuit 9634.
, A configuration including a DCDC converter 9636 is shown.

Note that since the tablet terminal can be folded in two, the housing 9630 can be closed when not in use. Accordingly, since the display portion 9631a and the display portion 9631b can be protected, a tablet terminal with excellent durability and high reliability can be provided from the viewpoint of long-term use.

In addition, the tablet terminal shown in FIGS. 10A and 10B has a function for displaying various information (still images, moving images, text images, etc.), a calendar, a date, or a time. A function for displaying on the display unit, a touch input function for performing touch input operation or editing of information displayed on the display unit, a function for controlling processing by various software (programs), and the like can be provided.

Electric power is displayed on a display portion 9631 by a solar battery 9633 attached to the surface of the tablet terminal.
(The display portion 9631a and / or the display portion 9631b), a touch panel in the display portion 9631, a video signal processing portion, and the like. Note that the solar battery 9633 is attached to the housing 96.
The battery 9635 is efficiently charged by being provided on at least one surface (for example, the surface on which the display portion 9631a and the display portion 9631b are provided is the entire back surface or a part thereof). Is preferable. Battery 96
As for 35, when a lithium ion battery is used, there is an advantage such as miniaturization.

Further, the structure and operation of the charge / discharge control circuit 9634 illustrated in FIG.
) Will be described with reference to a block diagram. FIG. 10C illustrates a solar cell 9633, a battery 96, and the like.
35, DCDC converter 9636, converter 9637, switches SW1 to SW3,
A display portion 9631 is shown, and a battery 9635 and a DCDC converter 9636 are shown.
The converter 9637 and the switches SW1 to SW3 are portions corresponding to the charge / discharge control circuit 9634 illustrated in FIG.

An example of operation in the case where power is generated by the solar battery 9633 using external light is described. The electric power generated by the solar battery 9633 becomes a voltage for charging the battery 9635 D
The CDC converter 9636 performs step-up or step-down. When power from the solar cell 9633 is used for the operation of the display portion 9631, the switch SW1 is turned on, and the converter 9637 increases or decreases the voltage required for the display portion 9631. In the case where display on the display portion 9631 is not performed, the battery 9635 may be charged by turning off SW1 and turning on SW2.

Note that the solar cell 9633 is described as an example of the power generation unit, but is not particularly limited, and the battery 9635 is charged by another power generation unit such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). There may be. For example, a non-contact power transmission module that wirelessly (contactlessly) transmits and receives power for charging and other charging means may be combined.

This example can be implemented in combination with any of the above embodiments as appropriate.

10 stages 80 stages 81 transistor 82 transistor 83 transistor 84 transistor 85 capacitive element 100 semiconductor device 101 transistor 102 transistor 103 transistor 104 transistor 105 transistor 106 transistor 107 transistor 108 transistor 109 transistor 110 transistor 211 capacitor element 212 capacitor element 400 substrate 402 gate electrode 404 Gate insulating layer 406 Oxide semiconductor layer 408 Oxide semiconductor layer 410 Transistor 412 Oxide semiconductor layer 414a Drain electrode 414b Source electrode 416 Gate insulating layer 418 Gate electrode 9630 Housing 9631 Display portion 9631a Display portion 9631b Display portion 9632a Region 9632b Region 9033 Fastener 9034 Display mode switch 035 power switch 9036 saving mode changeover switch 9037 operating keys 9038 operation switches 9639 keyboard display switching button 9633 solar cell 9634 charge and discharge control circuit 9635 battery 9636 DCDC converter 9637 Converter

Claims (5)

A first circuit, a first switch, and a second switch ;
The first circuit includes first to third transistors,
The first switch includes a fourth transistor;
The second switch includes a fifth transistor;
The first to fifth transistors have the same conductivity type,
One of a source and a drain of the first transistor is electrically connected to one of a source and a drain of the fifth transistor;
The other of the source and the drain of the fifth transistor is electrically connected to the first wiring;
A gate of the first transistor is electrically connected to a second wiring;
The other of the source and the drain of the first transistor is electrically connected to the gate of the second transistor;
A back gate of the first transistor is electrically connected to a gate of the second transistor;
One of a source and a drain of the second transistor is electrically connected to the second wiring;
The other of the source and the drain of the second transistor is electrically connected to a third wiring;
A back gate of the second transistor is electrically connected to the third wiring;
One of a source and a drain of the third transistor is electrically connected to the third wiring;
A gate of the third transistor is electrically connected to one of a source and a drain of the fourth transistor;
The other of the source and the drain of the fourth transistor is electrically connected to a fourth wiring;
The other of the source and the drain of the third transistor is electrically connected to a fifth wiring;
A back gate of the third transistor is electrically connected to the fifth wiring;
A gate of the fourth transistor is electrically connected to a sixth wiring;
A gate of the fifth transistor is electrically connected to the sixth wiring;
The sixth wiring has a function of supplying a clock signal;
The channel width of the first transistor is smaller than the channel width of the second transistor,
The channel width of the first transistor is smaller than the channel width of the third transistor,
The channel width of the fourth transistor is smaller than the channel width of the first transistor,
The channel width of the fourth transistor is smaller than the channel width of the second transistor,
A semiconductor device, wherein the channel width of the fourth transistor is smaller than the channel width of the third transistor. A first circuit, a second circuit, a first switch, and a second switch;
The first circuit includes first to third transistors,
The second circuit includes sixth to eighth transistors,
The first switch includes a fourth transistor;
The second switch includes a fifth transistor;
The first to eighth transistors have the same conductivity type,
One of a source and a drain of the first transistor is electrically connected to one of a source and a drain of the fifth transistor;
The other of the source and the drain of the fifth transistor is electrically connected to the first wiring;
A gate of the first transistor is electrically connected to a second wiring;
The other of the source and the drain of the first transistor is electrically connected to the gate of the second transistor;
A back gate of the first transistor is electrically connected to a gate of the second transistor;
One of a source and a drain of the second transistor is electrically connected to the second wiring;
The other of the source and the drain of the second transistor is electrically connected to a third wiring;
A back gate of the second transistor is electrically connected to the third wiring;
One of a source and a drain of the third transistor is electrically connected to the third wiring;
A gate of the third transistor is electrically connected to one of a source and a drain of the fourth transistor;
The other of the source and the drain of the fourth transistor is electrically connected to a fourth wiring;
The other of the source and the drain of the third transistor is electrically connected to a fifth wiring;
A back gate of the third transistor is electrically connected to the fifth wiring;
A gate of the fourth transistor is electrically connected to a sixth wiring;
A gate of the fifth transistor is electrically connected to the sixth wiring;
One of a source and a drain of the sixth transistor is electrically connected to one of a source and a drain of the fourth transistor;
A gate of the sixth transistor is electrically connected to the second wiring;
The other of the source and the drain of the sixth transistor is electrically connected to the gate of the seventh transistor;
A back gate of the sixth transistor is electrically connected to a gate of the seventh transistor;
One of a source and a drain of the seventh transistor is electrically connected to the second wiring;
The other of the source and the drain of the seventh transistor is electrically connected to a seventh wiring;
A back gate of the seventh transistor is electrically connected to the seventh wiring;
One of a source and a drain of the eighth transistor is electrically connected to the seventh wiring;
A gate of the eighth transistor is electrically connected to one of a source and a drain of the fifth transistor;
The other of the source and the drain of the eighth transistor is electrically connected to the fifth wiring;
A back gate of the eighth transistor is electrically connected to the fifth wiring;
The sixth wiring has a function of supplying a clock signal;
The channel width of the first transistor is smaller than the channel width of the second transistor,
The channel width of the first transistor is smaller than the channel width of the third transistor,
The channel width of the fourth transistor is smaller than the channel width of the first transistor,
The channel width of the fourth transistor is smaller than the channel width of the second transistor,
A semiconductor device, wherein the channel width of the fourth transistor is smaller than the channel width of the third transistor. In claim 2,
The semiconductor device, wherein a back gate of the fourth transistor is electrically connected to the fifth wiring. In any one of Claim 1 thru | or 3,
The first to third transistors each have a channel formed in an oxide semiconductor layer. In claim 4,
The method for manufacturing a semiconductor device, wherein the oxide semiconductor layer is formed through a process in which oxygen is supplied after dehydration or dehydrogenation treatment.

Images